Technical Practices for Sustainable Code 2019-09-14

Highly maintainable code is hard to produce.
Object oriented code was supposed to enable us to write clean, understandable code - and yet... we're often stuck with incomprehensible code we can't get tests around. Most of this isn't good object oriented code.
Good object oriented code is maintainable.
Writing good object oriented code is hard.
Without maintainability we can not have sustainable code, it will rot and have to be re-written. As an industry we're often given principles (DRY, SOLID, Abstraction, Code Reuse...) which sound great to have in out object oriented code. Knowing the principles is clearly not enough to enable us to write good object oriented code. We need some hands on keyboard deliberate practices that help us get there.
I just happen to write my code using some technical practices that drive good object-oriented code.
This talk goes into a few of technical practices I've found to have the biggest impact towards good object oriented code. Strictly applying just these practices will help the maintainability of the code.
These technical practices produce simple, understandable, testable code which results in extremely maintainable code that we can work in to consistently and quickly deliver value to our customers.

Transcript

1. Feature Parity in 25% of the Dev Hours with Technical Practices for Sustainable Code @TheQuinnGil QuinnGil.com
2. Feature Parity in 25% of the Dev Hours @TheQuinnGil QuinnGil.com
3. @TheQuinnGil QuinnGil.com Technical Practices for Sustainable Code
4. 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
5. This is for you. @TheQuinnGil QuinnGil.com
6. Sustainable Code through Technical Practices @TheQuinnGil QuinnGil.com
7. Sustainable Code through Technical Practices @TheQuinnGil QuinnGil.com
8. Sustainable Code through Technical Practices @TheQuinnGil QuinnGil.com
9. Tests @TheQuinnGil QuinnGil.com
10. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection
11. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection No Getters / No Setters @TheQuinnGil QuinnGil.com
12. Technical Practices - No Getters - Defined class FizzBuzzBag { public int Input { get; set; } public string Result { get; set; } } class FizzBuzzBag: def __init__(self): self._result = None self._input = None @property def result(self): return self._result @result.setter def result(self, value): self._result = value @property def input(self): return self._input @input.setter def input(self, value): self._input = value class FizzBuzzBag{ private int input; private String result; public String getResult(){ return result; } public void setResult(String value){ result = value; } public int getInput(){ return input; } public void setInput(int value){ input = value; } } class FizzBuzzBag attr_accessor :input attr_accessor :result end @TheQuinnGil QuinnGil.com
13. Technical Practices - No Getters No Getters? No Way! @TheQuinnGil QuinnGil.com
14. No Getters Technical Practices @TheQuinnGil QuinnGil.com
15. Technical Practices - No Getters Why No Getters? @TheQuinnGil QuinnGil.com
16. Technical Practices - No Getters How? @TheQuinnGil QuinnGil.com
17. Technical Practices - No Getters - How? The Class Does It @TheQuinnGil QuinnGil.com
18. Technical Practices - No Getters public class FizzBuzz{ public int Input { get; set; } public string Result { get; set; } } public static class FizzBuzzUtils{ public static void Calculate(FizzBuzz fb){ if (fb.Input % 3 == 0){ fb.Result = "Fizz"; } if (fb.Input % 5 == 0){ if (fb.Result == null){ fb.Result = "Buzz"; } else { fb.Result += "Buzz"; } } if (string.IsNullOrEmpty(fb.Result)){ fb.Result = fb.Input.ToString(); } } } @TheQuinnGil QuinnGil.com
19. Technical Practices - No Getters / No Setters public class FizzBuzz{ private readonly int _input; public FizzBuzz(int input) => _input = input; public string Result(){ string result = null; if (_input % 3 == 0) result = "Fizz"; if (_input % 5 == 0){ if (result == null) result = "Buzz"; else result += "Buzz"; } if (string.IsNullOrEmpty(result)){ result = _input.ToString(); } return result; } } public class FizzBuzz{ public int Input { get; set; } public string Result { get; set; } } public static class FizzBuzzUtils{ public static void Calculate(FizzBuzz fb){ if (fb.Input % 3 == 0){ fb.Result = "Fizz"; } if (fb.Input % 5 == 0){ if (fb.Result == null){ fb.Result = "Buzz"; } else { fb.Result += "Buzz"; } } if (string.IsNullOrEmpty(fb.Result)){ fb.Result = fb.Input.ToString(); } } } @TheQuinnGil QuinnGil.com
20. Technical Practices - No Getters / No Setters Benefits @TheQuinnGil QuinnGil.com
21. Sustainable Code through Technical Practices No Getters / No Setters @TheQuinnGil QuinnGil.com • No Getters / No Setters • `if` Only As Guard Clause • Isolate Their Code • Never `null` • No `new` inline • Composition, Not Inheritance • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection Sustainable Code from Encapsulating Behavior
22. Sustainable Code through Technical Practices `if` Only As Guard Clause @TheQuinnGil QuinnGil.com • No Getters / No Setters • `if` Only As Guard Clause • Isolate Their Code • Never `null` • No `new` inline • Composition, Not Inheritance • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection
23. Technical Practices - `if` Only As Guard Clause Guard Clause Only? No Way!
24. Technical Practices - `if` Only As Guard Clause Default Path @TheQuinnGil QuinnGil.com
25. `if` Only As Guard Clause - Default Path public class FizzBuzz{ private readonly int _input; public FizzBuzz(int input) => _input = input; public string Result(){ string result = null; if (_input % 3 == 0) result = "Fizz"; if (_input % 5 == 0){ if (result == null) result = "Buzz"; else result += "Buzz"; } if (string.IsNullOrEmpty(result)){ result = _input.ToString(); } return result; } } @TheQuinnGil QuinnGil.com
26. public class FizzBuzz{ private readonly int _input; public FizzBuzz(int input) => _input = input; public string Result(){ string result = null; if (_input % 3 == 0) result = "Fizz"; if (_input % 5 == 0){ if (result == null) result = "Buzz"; else result += "Buzz"; } if (string.IsNullOrEmpty(result)){ result = _input.ToString(); } return result; } } `if` Only As Guard Clause - Default Path public class FizzBuzz{ private int _input; public FizzBuzz(int input) => _input = input; public string Result(){ if (_input % 15 == 0) return "FizzBuzz"; if (_input % 3 == 0) return "Fizz"; if (_input % 5 == 0) return "Buzz"; return _input.ToString(); } } @TheQuinnGil QuinnGil.com
27. Technical Practices - `if` Only As Guard Clause Cascading Changes @TheQuinnGil QuinnGil.com
28. Technical Practices - `if` Only As Guard Clause Cascading Changes switch and else - always evil @TheQuinnGil QuinnGil.com
29. Technical Practices - `if` Only As Guard Clause How? @TheQuinnGil QuinnGil.com
30. `if` Only As Guard Clause - Default Path public class FizzBuzz{ private int _input; public FizzBuzz(int input) => _input = input; public string Result(){ if (_input % 15 == 0) return "FizzBuzz"; if (_input % 3 == 0) return "Fizz"; if (_input % 5 == 0) return "Buzz"; return _input.ToString(); } } public class FizzBuzz{ private readonly int _input; public FizzBuzz(int input) => _input = input; public string Result(){ string result = null; if (_input % 3 == 0) result = "Fizz"; if (_input % 5 == 0){ if (result == null) result = "Buzz"; else result += "Buzz"; } if (string.IsNullOrEmpty(result)){ result = _input.ToString(); } return result; } } @TheQuinnGil QuinnGil.com
31. Sustainable Code through Technical Practices `if` Only As Guard Clause @TheQuinnGil QuinnGil.com • No Getters / No Setters • `if` Only As Guard Clause • Isolate Their Code • Never `null` • No `new` inline • Composition, Not Inheritance • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection Sustainable Code from Limited Branching; Smaller Methods; Encapsulated Behavior Decisions
32. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection
33. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
34. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
35. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
36. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
37. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
38. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); //EXCEPTION return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
39. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
40. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
41. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
42. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
43. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> NetworkCall(HttpRequestMessage r) { IHttpResponseMessageBookEnd httpResponseMessage = await _httpClient.SendAsync(r); string readAsStringAsync = await httpResponseMessage.ContentAsStringAsync(); JObject jsonContent = JObject.Parse(readAsStringAsync); string value = jsonContent.Value<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } @TheQuinnGil QuinnGil.com
44. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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
45. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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
46. Technical Practices - Isolate Their Code - 3rd Party public async Task<string> 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<string>("some_key"); return value.Contains("expected_Value") ? "Success" : "Failure"; } public async Task<string> 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
47. What Else? Technical Practices - Isolate Their Code @TheQuinnGil QuinnGil.com
48. Operating System Technical Practices - Isolate Their Code @TheQuinnGil QuinnGil.com
49. How? Technical Practices - Isolate Their Code @TheQuinnGil QuinnGil.com
50. Technical Practices - Isolate Their Code - How? HttpClient httpClient = new HttpClient(); @TheQuinnGil QuinnGil.com IHttpClientBookEnd httpClient = new HttpClientFacade();
51. 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<IHttpResponseMessageBookEnd> SendRequestAsync(HttpRequestMessage msg) => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg)); private HttpClient HttpClient() => _testClient ?? _httpClient; } @TheQuinnGil QuinnGil.com
52. 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<IHttpResponseMessageBookEnd> SendRequestAsync(HttpRequestMessage msg) => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg)); private HttpClient HttpClient() => _testClient ?? _httpClient; } @TheQuinnGil QuinnGil.com
53. 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<IHttpResponseMessageBookEnd> SendRequestAsync(HttpRequestMessage msg) => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg)); private HttpClient HttpClient() => _testClient ?? _httpClient; } @TheQuinnGil QuinnGil.com
54. 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<IHttpResponseMessageBookEnd> SendRequestAsync(HttpRequestMessage msg) => new HttpResponseMessageAdapter(await HttpClient().SendAsync(msg)); private HttpClient HttpClient() => _testClient ?? _httpClient; } @TheQuinnGil QuinnGil.com
55. User Interface Technical Practices - Isolate Their Code @TheQuinnGil QuinnGil.com
56. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection Sustainable Code from Full Testability; Narrow Scope of Change; Reduced Complexity
57. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection
58. Feature Parity in 25% of the Dev Hours @TheQuinnGil QuinnGil.com
59. THANK YOU! @TheQuinnGil QuinnGil.com
60. 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 • <Strong opinions loosely held> • Be Immutable • No Primitives • Extract Cohesion • No Public Statics • Never Reflection @TheQuinnGil QuinnGil.com