- GO does not have class. However, we can define methods on types.
- A method is a function with a special receiver argument.
- The receiver appears in its own argument list between the
funckeyword 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.
-
- Interfaces
- 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. AStringeris a type that can describe itself as a string. Thefmtpkg look for this interface to print values.
type Stringer interface {
String() string
}
- Error
- The error type is a built-in interface similar to
fmt.Stringer.
type error interface{
Error() string
}
- Readers
- The IO package specifies the
io.Readerinterface, which denote the read end of a stream of data.
- HTTP servers
*Packagehttpserves HTTP request using any value that implementshttp.Handler: - Image
- Package image defines the
Imageinterface.
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