A Tour of GO (4) -- Methods and

2016-01-13 本文已影响0人陈胖子胖胖胖

A method is a function with a special receiver argument.
The receiver appears in its own argument list between the func keyword and the method name.
func (v Vertex) Abs() float64 {
return math.Sqrt(v.Xv.X + v.Yv.Y)
}
Remember: A method is just a function with a receiver argument. This one functions the same as the previous one.
func Abs(v Vertex) float64 {
return math.Sqrt(v.Xv.X + v.Yv.Y)
}
Important: You can only declare a method with a receiver whose type is defined in the same package. That includes the built-in type. However you can use
type MyFloat float64
Pointer receivers:
func (v *Vertex) Scale(f float64) {
v.X = v.X * f
v.Y = v.Y * f
}
- Method with pointer receivers can modify the value to which the receiver points. ( GO is passing by value by default)
- Method and pointer indirection. Method will be called automatically even v is a value not a pointer, but function will not.
  var v Vertex
  /* Method /
  v.Scale(5) // OK
  p := &v
  p.Scale(10) // OK
  / function */
  ScaleFunc(v) // Compile error!
  ScaleFunc(&v) // OK
- The equivalent thing happens int the reverse direction. The method takes value as receiver can also takes pointer while function cannot.
- Using pointer as receiver is encouraged. In general, all methods on a give type should have either value or pointer receivers, but not a mixture of both.

An interface type is defined by a set of methods.
type Abser interface {
Abs() float64
}
A type implements an interface by implementing the methods.
Stringer. A Stringer is a type that can describe itself as a string. The fmt pkg look for this interface to print values.
type Stringer interface {
String() string
}

The error type is a built-in interface similar to fmt.Stringer.
type error interface{
Error() string
}

The IO package specifies the io.Readerinterface, which denote the read end of a stream of data.

HTTP servers
*Package http serves HTTP request using any value that implements http.Handler:
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