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Things I learned
teaching Go
Francesc Campoy
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Adoption
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Making Go easy to learn
- live workshops
- online resources
- the Go tour
- blog posts
- documentation
- talks
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Learning a new language
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I caught a cold
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estoy constipado
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je suis …
I am ...
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False Friends
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Java iterating over a collection
for (Thing thing: things)
Go iterating over a slice
for thing := range things
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Java iterating over a collection
for (Thing thing: things)
Go iterating over a slice
for thing := range things
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Java iterating over a collection
for (Thing thing: things)
Go iterating over a slice
for _, thing := range things
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“Like Yoda speaks
code you must not”
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Idiomatic Go code
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Foreign influence
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type Vertex struct {
x, y int
}
func (this *Vertex) Abs() float64 {
x, y := this.GetX(), this.GetY()
return math.Sqrt(x*x + y*y)
}
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type Vertex struct {
x, y int
}
func (this *Vertex) Abs() float64 {
x, y := this.GetX(), this.GetY()
return math.Sqrt(x*x + y*y)
}
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No content
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type Vertex struct {
_x, _y int
}
func (self *Vertex) Abs() float64 {
x, y := self._x, self._y
return math.Sqrt(x*x + y*y)
}
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type Vertex struct {
_x, _y int
}
func (self *Vertex) Abs() float64 {
x, y := self._x, self._y
return math.Sqrt(x*x + y*y)
}
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No content
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type Vertex struct {
x, y int
}
func (v *Vertex) Abs() float64 {
x, y := v.x, v.y
return math.Sqrt(x*x + y*y)
}
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Things that are hard to learn
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Eyjafjallajökull
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No content
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Interfaces
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type Stringer interface {
String() string
}
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Set of constraints on types
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type Stringer interface {
String() string
}
type myCoolStringer interface {
String() string
}
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type Reader interface {
Read([]byte) (int, error)
}
type Writer interface {
Write([]byte) (int, error)
}
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type ReadWriter interface {
Reader
Writer
}
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Reader
gzip.Reader
rand.Reader
ReadWriter
*os.File
net.Conn
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Reader
gzip.Reader
rand.Reader
Writer
gzip.Writer
log.Writer
ReadWriter
*os.File
net.Conn
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Writer
ReadWriter
???
Reader
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interface{}
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method set (I) ⊆ method set (T)
Implicit satisfaction
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Method sets
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The method set of any other type T consists of all
methods declared with receiver type T.
The method set of a pointer type *T is the set of all
methods declared with receiver *T or T.
The method set of an interface type is its interface
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The method set of any other type T consists of all
methods declared with receiver type T.
The method set of a pointer type *T is the set of all
methods declared with receiver *T or T.
The method set of an interface type is its interface
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The method set of any other type T consists of all
methods declared with receiver type T.
The method set of a pointer type *T is the set of all
methods declared with receiver *T or T.
The method set of an interface type is its interface
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type Person struct {
Name string
Age int
}
func (p *Person) String() string {
return fmt.Sprintf("%s is %d", p.Name, p.Age)
}
func main() {
p := &Person{"Hillary", 66}
fmt.Println(p)
}
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type Person struct {
Name string
Age int
}
func (p *Person) String() string {
return fmt.Sprintf("%s is %d", p.Name, p.Age)
}
func main() {
p := &Person{"Hillary", 66}
fmt.Println(p)
}
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Hillary is 66 years old
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type Person struct {
Name string
Age int
}
func (p Person) String() string {
return fmt.Sprintf("%s is %d", p.Name, p.Age)
}
func main() {
p := &Person{"Hillary", 66}
fmt.Println(p)
}
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Hillary is 66 years old
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The method set of any other type T consists of all
methods declared with receiver type T.
The method set of a pointer type *T is the set of all
methods declared with receiver *T or T.
The method set of an interface type is its interface
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type Person struct {
Name string
Age int
}
func (p Person) String() string {
return fmt.Sprintf("%s is %d", p.Name, p.Age)
}
func main() {
p := Person{"Hillary", 66}
fmt.Println(p)
}
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Hillary is 66 years old
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type Person struct {
Name string
Age int
}
func (p *Person) String() string {
return fmt.Sprintf("%s is %d", p.Name, p.Age)
}
func main() {
p := Person{"Hillary", 66}
fmt.Println(p)
}
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{Hillary 66}
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func (T) Foo() func (*T) Foo()
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func (T) Foo() func (*T) Foo()
T → T *T → *T
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func (T) Foo() func (*T) Foo()
T → T *T → *T
*T → T
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func (T) Foo() func (*T) Foo()
T → T *T → *T
*T → T T → *T
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&42
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func (T) Foo() func (*T) Foo()
T → T *T → *T
*T → T T ↛ *T
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*T T
func (T) Foo() func (T) Foo()
func (*T) Foo()
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No content
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nil
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var s fmt.Stringer
fmt.Println(s, s == nil)
# , true
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var p *Person
var s fmt.Stringer = p
fmt.Println(p, p == nil)
fmt.Println(s, s == nil)
# true
# false
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(type, value)
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var p *Person
var s fmt.Stringer = p
fmt.Printf(“%#v”, s)
# (*main.Person)(nil)
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(*Person, nil)
doesn’t equal nil
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var s fmt.Stringer
fmt.Printf(“%#v”, s)
#
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(nil, nil)
equals nil
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When nil is not nil
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func do() error {
var err *doError
…
return err
}
func main() {
if err := do(); err != nil {
fmt.Println(err)
}
}
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func do() error {
var err *doError
…
return err
}
func main() {
if err := do(); err != nil {
fmt.Println(err)
}
}
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Other hard things
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How do I learn Go?
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read the specs often, really
Know the basics
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write code
Immersion
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share your code and ask for feedback
Immersion
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false friends and idioms
Don’t be embarrassed
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Always pass on what you
have learned
- Yoda
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Adoption
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@francesc
Merci
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- Eyjafjallajökull By Boaworm (Own work) CC-BY-3.0 via Wikimedia
Commons
- Yoda picture “Save you it can.” by JD Hancock is licensed under a
Creative Commons Attribution 3.0
- Chinese letters by Michael Coghlan is licensed under a Creative
Commons Attribution 3.0
Attributions