Trust Your Code - Don't Be Defensive 2019-09-14

Trust Your Code - Don't defend it.

We are trained to code defensively.
We have to defend our method against getting a bad result as a return argument.
We have to defend their method from being called when it shouldn't.
We have to defend ourselves against being passed unusable parameter.

We are so focused on defending and trying to know how everything our method uses works that we become numb to the damage we're inflicting on the source code itself.

Let's trust our code.
Let's trust the return value is something we can use.
Let's trust the method knows if it should execute or not.
Let's trust that the parameter we're given is usable.

Trusting our code simplifies our code.

This trust isn't free.
This trust takes discipline and rigor.
This trust takes practices that allow us to have this trust.

This talk is about the practices that enable us to trust our code and not be so defensive about it.

Transcript

1. Trust Your Code
   @TheQuinnGil QuinnGil.com
   Seattle Code Camp 2019
   

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2. Quinn Gil
   Software Development Coach
   International Speaker on Software Development
   Past 15 years focused on High Quality code
   Blog at QuinnGil.com
   @TheQuinnGil QuinnGil.com
   

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3. This is for you.
   @TheQuinnGil QuinnGil.com
   

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4. Trust Your Code
   @TheQuinnGil QuinnGil.com
   

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5. “Untrusted Code”?
   @TheQuinnGil QuinnGil.com
   

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6. Untrusted Code - Defensive Code
   ● Defend the Method Perspective
   ○ PreConditions
   ○ Nulls
   ○ Assertions
   @TheQuinnGil QuinnGil.com
   

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7. Untrusted Code - Defenses
   ● Defend the Method Perspective
   ○ PreConditions
   ○ Nulls
   ○ Assertions
   ● Defend the Caller Perspective
   ○ State Verification
   ○ Exception Handling
   ○ OK to call
   @TheQuinnGil QuinnGil.com
   

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8. Untrusted Code - Defenses
   ● Defend the Method Perspective
   ○ PreConditions
   ○ Nulls
   ○ Assertions
   ● Defend the Caller Perspective
   ○ State Verification
   ○ Exception Handling
   ○ OK to call
   ● Defend the Using Perspective
   ○ Null
   ○ Ready
   ○ Valid
   @TheQuinnGil QuinnGil.com
   

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9. Is “Defensive Code”
   really that bad?
   @TheQuinnGil QuinnGil.com
   

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10. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    @TheQuinnGil QuinnGil.com
    

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11. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    ● Complicates the code
    @TheQuinnGil QuinnGil.com
    

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12. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    ● Complicates the code
    ● Higher Cognitive Load
    @TheQuinnGil QuinnGil.com
    

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13. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    ● Complicates the code
    ● Higher Cognitive Load
    ● Write more code
    @TheQuinnGil QuinnGil.com
    

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14. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    ● Complicates the code
    ● Higher Cognitive Load
    ● Write more code
    ● Maintain more code
    @TheQuinnGil QuinnGil.com
    

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15. Why not “Defensive Code”?
    ● A defense somewhere is a defense everywhere
    ● Complicates the code
    ● Higher Cognitive Load
    ● Write more code
    ● Maintain more code
    ● Dead Code? Undetectable?
    @TheQuinnGil QuinnGil.com
    

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16. How do we protect the code?
    @TheQuinnGil QuinnGil.com
    

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17. How do we protect the code?
    @TheQuinnGil QuinnGil.com
    I don’t
    

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18. How do we protect the code?
    @TheQuinnGil QuinnGil.com
    I don’t... directly.
    

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19. Trust Your Code
    with
    Technical Practices
    @TheQuinnGil QuinnGil.com
    

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20. Trusting Your Code
    is
    Sustainable Code
    @TheQuinnGil QuinnGil.com
    

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21. Sustainable Code
    through
    Technical Practices
    @TheQuinnGil QuinnGil.com
    

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22. Sustainable Code
    through
    Technical Practices
    @TheQuinnGil QuinnGil.com
    

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23. Sustainable Code
    through
    Technical Practices
    @TheQuinnGil QuinnGil.com
    

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24. Tests
    @TheQuinnGil QuinnGil.com
    

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25. Sustainable Code through Technical Practices
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    @TheQuinnGil QuinnGil.com
    

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26. Sustainable Code through Technical Practices
    Isolate Their Code
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    

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27. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    HttpClient httpClient = new HttpClient();
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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28. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    //COUPLING
    HttpClient httpClient = new HttpClient();
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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29. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    //COUPLING
    HttpClient httpClient = new HttpClient();
    //EXCEPTION
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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30. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    //COUPLING
    HttpClient httpClient = new HttpClient();
    //EXCEPTION
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    //EXCEPTION, COUPLING
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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31. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    //COUPLING
    HttpClient httpClient = new HttpClient();
    //EXCEPTION
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    //EXCEPTION, COUPLING
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    //IMPERATIVE
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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32. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    //COUPLING
    HttpClient httpClient = new HttpClient();
    //EXCEPTION
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    //EXCEPTION, COUPLING
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    //IMPERATIVE
    string value = jsonContent.Value("some_key");
    //EXCEPTION
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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33. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    HttpClient httpClient = new HttpClient();
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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34. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpClientBookEnd httpClient = new HttpClientFacade();
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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35. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpClientBookEnd httpClient = new HttpClientFacade();
    IHttpResponseMessageBookEnd httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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36. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpClientBookEnd httpClient = new HttpClientFacade();
    IHttpResponseMessageBookEnd httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.ContentAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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37. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpResponseMessageBookEnd httpResponseMessage = await _httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.ContentAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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38. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpResponseMessageBookEnd httpResponseMessage = await _httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.ContentAsStringAsync();
    IParsedObject parsedObject = _parser.Parse(readAsStringAsync);
    string value = parsedObject.StringValue("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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39. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpResponseMessageBookEnd httpResponseMessage = await _httpClient.SendAsync(r);
    IParsedObject parsedObject = await httpResponseMessage.ParsedContent(_parser);
    string value = parsedObject.StringValue("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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40. Technical Practices - Isolate Their Code - 3rd Party
    public async Task NetworkCall(HttpRequestMessage r)
    {
    HttpClient httpClient = new HttpClient();
    HttpResponseMessage httpResponseMessage = await httpClient.SendAsync(r);
    string readAsStringAsync = await httpResponseMessage.Content.ReadAsStringAsync();
    JObject jsonContent = JObject.Parse(readAsStringAsync);
    string value = jsonContent.Value("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    public async Task NetworkCall(HttpRequestMessage r)
    {
    IHttpResponseMessageBookEnd httpResponseMessage = await _httpClient.SendAsync(r);
    IParsedObject parsedObject = await httpResponseMessage.ParsedContent(_parser);
    string value = parsedObject.StringValue("some_key");
    return value.Contains("expected_Value") ? "Success" : "Failure";
    }
    @TheQuinnGil QuinnGil.com
    

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41. What Else?
    Technical Practices - Isolate Their Code
    @TheQuinnGil QuinnGil.com
    

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42. Operating System
    Technical Practices - Isolate Their Code
    @TheQuinnGil QuinnGil.com
    

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43. How?
    Technical Practices - Isolate Their Code
    @TheQuinnGil QuinnGil.com
    

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44. Technical Practices - Isolate Their Code - How?
    internal class HttpClientFacade : IHttpClientBookEnd
    {
    private static HttpClient _testClient;
    #if DEBUG
    public static void SetTestClient(HttpClient testClient) => _testClient = testClient;
    #endif
    private readonly HttpClient _httpClient;
    public HttpClientFacade() : this(new HttpClient()) { }
    private HttpClientFacade(HttpClient httpClient) => _httpClient = httpClient;
    public async Task SendRequestAsync(HttpRequestMessage msg)
    => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg));
    private HttpClient HttpClient() => _testClient ?? _httpClient;
    }
    @TheQuinnGil QuinnGil.com
    

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45. Technical Practices - Isolate Their Code - How?
    internal class HttpClientFacade : IHttpClientBookEnd
    {
    private static HttpClient _testClient;
    #if DEBUG
    public static void SetTestClient(HttpClient testClient) => _testClient = testClient;
    #endif
    private readonly HttpClient _httpClient;
    public HttpClientFacade() : this(new HttpClient()) { }
    private HttpClientFacade(HttpClient httpClient) => _httpClient = httpClient;
    public async Task SendRequestAsync(HttpRequestMessage msg)
    => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg));
    private HttpClient HttpClient() => _testClient ?? _httpClient;
    }
    @TheQuinnGil QuinnGil.com
    

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46. Technical Practices - Isolate Their Code - How?
    internal class HttpClientFacade : IHttpClientBookEnd
    {
    private static HttpClient _testClient;
    #if DEBUG
    public static void SetTestClient(HttpClient testClient) => _testClient = testClient;
    #endif
    private readonly HttpClient _httpClient;
    public HttpClientFacade() : this(new HttpClient()) { }
    private HttpClientFacade(HttpClient httpClient) => _httpClient = httpClient;
    public async Task SendRequestAsync(HttpRequestMessage msg)
    => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg));
    private HttpClient HttpClient() => _testClient ?? _httpClient;
    }
    @TheQuinnGil QuinnGil.com
    

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47. Technical Practices - Isolate Their Code - How?
    internal class HttpClientFacade : IHttpClientBookEnd
    {
    private static HttpClient _testClient;
    #if DEBUG
    public static void SetTestClient(HttpClient testClient) => _testClient = testClient;
    #endif
    private readonly HttpClient _httpClient;
    public HttpClientFacade() : this(new HttpClient()) { }
    private HttpClientFacade(HttpClient httpClient) => _httpClient = httpClient;
    public async Task SendRequestAsync(HttpRequestMessage msg)
    => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg));
    private HttpClient HttpClient() => _testClient ?? _httpClient;
    }
    @TheQuinnGil QuinnGil.com
    

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48. User Interface
    Technical Practices - Isolate Their Code
    @TheQuinnGil QuinnGil.com
    

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49. Sustainable Code through Technical Practices
    Isolate Their Code
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    Trust Your Code by controlling interactions with 3rd Party Code
    

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50. Sustainable Code through Technical Practices
    Never `null`
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    

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51. Why?
    Technical Practices - Never `null`
    @TheQuinnGil QuinnGil.com
    

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52. How?
    Technical Practices - Never `null`
    @TheQuinnGil QuinnGil.com
    

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53. Technical Practices - Never `null`
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    @TheQuinnGil QuinnGil.com
    

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54. Technical Practices - Never `null`
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    public string CalculateThing(ICanBeNull canBeNull)
    {
    return canBeNull?.Example()?.Sample() ?? "Default";
    }
    @TheQuinnGil QuinnGil.com
    

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55. Technical Practices - Never `null`
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    public string CalculateThing(ICanBeNull canBeNull)
    {
    return canBeNull?.Example()?.Sample() ?? "Default";
    }
    public string CalculateThing(ICanNotBeNull canNotBeNull)
    {
    return canNotBeNull.Example().Sample();
    }
    @TheQuinnGil QuinnGil.com
    

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56. Technical Practices - Never `null`
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    public string CalculateThing(ICanBeNull canBeNull)
    {
    return canBeNull?.Example()?.Sample() ?? "Default";
    }
    public string CalculateThing(ICanNotBeNull canNotBeNull)
    {
    return canNotBeNull.Example().Sample();
    }
    public void Foo()
    {
    string thing = _bar.CalculateThing(_canBeNull);
    //...
    }
    @TheQuinnGil QuinnGil.com
    

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57. Technical Practices - Never `null`
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    public string CalculateThing(ICanBeNull canBeNull)
    {
    return canBeNull?.Example()?.Sample() ?? "Default";
    }
    public string CalculateThing(ICanNotBeNull canNotBeNull)
    {
    return canNotBeNull.Example().Sample();
    }
    public void Foo()
    {
    string thing = _bar.CalculateThing(_canBeNull);
    //...
    }
    public void Foo()
    {
    string thing = _canNotBeNull.Example().Sample();
    //...
    }
    @TheQuinnGil QuinnGil.com
    

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58. Technical Practices - Never `null`
    public class NullObject : ICanNotBeNull
    {
    public IAlsoNotNull Example() => new NullObjectAlso();
    }
    public class NullObjectAlso : IAlsoNotNull
    {
    public string Sample() => "Default";
    }
    public string CalculateThing(ICanBeNull canBeNull)
    {
    if (canBeNull == null) return "Default";
    IAlsoNull alsoNull = canBeNull.Example();
    if (alsoNull == null) return "Default";
    string sample = alsoNull.Sample();
    if (sample == null) return "Default";
    return sample;
    }
    public void Foo()
    {
    string thing = _canNotBeNull.Example().Sample();
    //...
    }
    @TheQuinnGil QuinnGil.com
    

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59. Sustainable Code through Technical Practices
    Never `null`
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    Trust Your Code by always having valid objects
    

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60. Sustainable Code through Technical Practices
    No Primitives
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    

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61. Primitives?
    Technical Practices - No Primitives
    @TheQuinnGil QuinnGil.com
    

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62. Technical Practices - What are Primitives?
    ● Data (string, int, double, float, ...)
    @TheQuinnGil QuinnGil.com
    

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63. Technical Practices - What are Primitives?
    ● Data (string, int, double, float, ...)
    ● Collections (List, Map, Dictionary, ...)
    @TheQuinnGil QuinnGil.com
    

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64. Technical Practices - What are Primitives?
    ● Data (string, int, double, float, ...)
    ● Collections (List, Map, Dictionary, ...)
    ● Enums
    @TheQuinnGil QuinnGil.com
    

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65. Technical Practices - What are Primitives?
    ● Data (string, int, double, float, ...)
    ● Collections (List, Map, Dictionary, ...)
    ● Enums
    ● More?
    @TheQuinnGil QuinnGil.com
    

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66. Why not Primitives?
    Technical Practices - No Primitives
    @TheQuinnGil QuinnGil.com
    

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67. ● Object oriented programming wants object interaction, not data manipulation
    Technical Practices - Why No Primitives?
    @TheQuinnGil QuinnGil.com
    

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68. ● Object oriented programming wants object interaction, not data manipulation
    ● Primitives are data, not objects
    Technical Practices - Why No Primitives?
    @TheQuinnGil QuinnGil.com
    

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69. ● Object oriented programming wants object interaction, not data manipulation
    ● Primitives are data, not objects
    ● Primitives force complex imperative code
    Technical Practices - Why No Primitives?
    @TheQuinnGil QuinnGil.com
    

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70. ● Object oriented programming wants object interaction, not data manipulation
    ● Primitives are data, not objects
    ● Primitives force complex imperative code
    ● Primitives hinder Emergent Design
    Technical Practices - Why No Primitives?
    @TheQuinnGil QuinnGil.com
    

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71. ● Object oriented programming wants object interaction, not data manipulation
    ● Primitives are data, not objects
    ● Primitives force complex imperative code
    ● Primitives hinder Evolutionary Architecture
    ● Primitives limit use of Design Patterns
    Technical Practices - Why No Primitives?
    @TheQuinnGil QuinnGil.com
    

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72. Instead?
    Technical Practices - No Primitives
    @TheQuinnGil QuinnGil.com
    

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73. Represent the Concept
    Technical Practices - No Primitives
    @TheQuinnGil QuinnGil.com
    

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74. Technical Practices - No Primitives - Age Example
    public bool ThirteenOrLess(DataPerson person)
    {
    DateTime birthDate = DateTime.Parse(person.BirthDate);
    int age = DateTime.Now.Year - birthDate.Year;
    /* is this right?*/
    return age <= 13;
    }
    @TheQuinnGil QuinnGil.com
    

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75. public bool ThirteenOrLess(DataPerson person)
    {
    DateTime birthDate = DateTime.Parse(person.BirthDate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    return age <= 13;
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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76. public bool ThirteenOrLess(DataPerson person)
    {
    DateTime birthDate = DateTime.Parse(person.BirthDate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    switch (person.State)
    {
    case "WA":
    return age <= 13;
    case "AK":
    return age <= 14;
    }
    return false;
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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77. public bool IsMinor(DataPerson person)
    {
    DateTime birthDate = DateTime.Parse(person.BirthDate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    switch (person.State)
    {
    case "WA":
    return age <= 13;
    case "AK":
    return age <= 14;
    }
    return false;
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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78. public class Age : IAge
    {
    public bool IsMinor()
    {
    DateTime birthDate = DateTime.Parse(_birthdate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    switch (_state)
    {
    case "WA":
    return age <= 13;
    case "AK":
    return age <= 14;
    }
    return false;
    }
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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79. public class Age : IAge
    {
    public bool IsMinor()
    {
    DateTime birthDate = DateTime.Parse(_birthdate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    switch (_state)
    {
    case "WA":
    return age <= 13;
    case "AK":
    return age <= 14;
    }
    return false;
    }
    }
    public class Person
    {
    private readonly string _birthdate;
    private readonly string _state;
    public IAge Age() => new Age(_birthdate, _state);
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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80. public class Age : IAge
    {
    public bool IsMinor()
    {
    DateTime birthDate = DateTime.Parse(_birthdate);
    int age = DateTime.Now.Year - birthDate.Year;
    if (birthDate.Date > DateTime.Now.AddYears(-age)) age--;
    return age <= _state.MinorAge();
    }
    }
    public class Person
    {
    private readonly string _birthdate;
    private readonly State _state;
    public IAge Age() => new Age(_birthdate, _state);
    }
    @TheQuinnGil QuinnGil.com
    Technical Practices - No Primitives - Age Example
    

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81. Technical Practices - No Primitives - Age Example
    @TheQuinnGil QuinnGil.com
    Represent the Concept
    

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82. Technical Practices - No Primitives - Units
    public float Convert(float value)
    @TheQuinnGil QuinnGil.com
    

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83. Technical Practices - No Primitives - Units
    public float Convert(float value)
    {
    return value * 1.609334f;
    }
    @TheQuinnGil QuinnGil.com
    

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84. Technical Practices - No Primitives - Units
    public float Convert(float value)
    {
    return value * 1.609334f;
    }
    Money?
    @TheQuinnGil QuinnGil.com
    

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85. Technical Practices - No Primitives - Units
    public float Convert(float value)
    {
    return value * 1.609334f;
    }
    Money? Distance?
    @TheQuinnGil QuinnGil.com
    

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86. Technical Practices - No Primitives - Units
    public float Convert(float value)
    {
    return value * 1.609334f;
    }
    @TheQuinnGil QuinnGil.com
    Money? Distance?
    Convert To? From?
    

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87. Technical Practices - No Primitives - Units
    public float Convert(float distance)
    {
    return distance * 1.609334f;
    }
    Missing Meta Data
    Convert To? From?
    @TheQuinnGil QuinnGil.com
    Money? Distance?
    

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88. Technical Practices - No Primitives - Units
    public class Distance
    ...
    distance.ToKilometer();
    ...
    With Meta Data
    @TheQuinnGil QuinnGil.com
    

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89. Technical Practices - No Primitives - Age Example
    @TheQuinnGil QuinnGil.com
    Represent the Concept
    

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90. Sustainable Code through Technical Practices
    No Primitives
    @TheQuinnGil QuinnGil.com
    Trust Your Code by having objects represent the concepts in the code
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    

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91. Sustainable Code through Technical Practices
    @TheQuinnGil QuinnGil.com
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    

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92. Feature Parity in
    25% of the Dev Hours
    @TheQuinnGil QuinnGil.com
    

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93. THANK YOU!
    @TheQuinnGil QuinnGil.com
    

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94. Sustainable Code through Technical Practices
    ● No Getters / No Setters
    ● `if` Only As Guard Clause
    ● Isolate Their Code
    ● Never `null`
    ● No `new` inline
    ● Composition, Not Inheritance
    ●
    ● Be Immutable
    ● No Primitives
    ● Extract Cohesion
    ● No Public Statics
    ● Never Reflection
    @TheQuinnGil QuinnGil.com
    

    View Slide