go基本语法学习笔记之面向对象:接口

type File struct {
 // ...
}
func (f *File) Read(buf []byte) (n int, err error)
func (f *File) Write(buf []byte) (n int, err error)
func (f *File) Seek(off int64, whence int) (pos int64, err error)
func (f *File) Close() error

type IFile interface {
 Read(buf []byte) (n int, err error)
 Write(buf []byte) (n int, err error)
 Seek(off int64, whence int) (pos int64, err error)
 Close() error
}

type IReader interface {
 Read(buf []byte) (n int, err error)
}
type IWriter interface {
 Write(buf []byte) (n int, err error)
}
type ICloser interface {
 Close() error
}

var file1 IFile = new(File)
var file2 IReader = new(File)
var file3 IWriter = new(File)
var file4 ICloser = new(File)

接口赋值

1. 将对象实例赋值给接口;
2. 将一个接口赋值给另一个接口。

type Integer int
<pre name="code" class="plain">func (a Integer) Less(b Integer) bool {
 return a < b
}

type LessAdder interface {
 Less(b Integer) bool
 Add(b Integer)
}

var a Integer = 1
var b LessAdder = &a ... (1)ok <span style="font-family: Arial, Helvetica, sans-serif;">
</span>var b LessAdder = a ... (2)no

</pre><pre name="code" class="plain">GO可以根据
func (a Integer) Less(b Integer) bool
自动生成新方法
func (a *Integer) Less(b Integer) bool {
 return (*a).Less(b)
}

接口查询

var file1 Writer = ...
if file5, ok := file1.(two.IStream); ok {
 ...
}

var file1 Writer = ...
if file6, ok := file1.(*File); ok { //这个if语句判断file1接口指向的对象实例是否是*File类型
 ...
}

var v1 interface{} = ...
switch v := v1.(type) {
 case int: // 现在v的类型是int
 case string: // 现在v的类型是string
 ...
}

//接口中可以组合其它接口,这种方式等效于在接口中添加其它接口的方法
type Reader interface {
	read()
}
type Writer interface {
	write()
}
//定义上述两个接口的实现类
type MyReadWrite struct{}
func (mrw *MyReadWrite) read() {
	fmt.Println("MyReadWrite...read")
}
func (mrw *MyReadWrite) write() {
	fmt.Println("MyReadWrite...write")
}
//定义一个接口,组合了上述两个接口
type ReadWriter interface {
	Reader
	Writer
}
//上述接口等价于:
type ReadWriterV2 interface {
	read()
	write()
}
//ReadWriter和ReadWriterV2两个接口是等效的,因此可以相互赋值
func interfaceTest0104() {
	mrw := &MyReadWrite{}
	//mrw对象实现了read()方法和write()方法,因此可以赋值给ReadWriter和ReadWriterV2
	var rw1 ReadWriter = mrw
	rw1.read()
	rw1.write()
	fmt.Println("------")
	var rw2 ReadWriterV2 = mrw
	rw2.read()
	rw2.write()
	//同时,ReadWriter和ReadWriterV2两个接口对象可以相互赋值
	rw1 = rw2
	rw2 = rw1
}

var v1 interface{} = 1 // 将int类型赋值给interface{}
var v2 interface{} = "abc" // 将string类型赋值给interface{}
var v3 interface{} = &v2 // 将*interface{}类型赋值给interface{}
var v4 interface{} = struct{ X int }{1}
var v5 interface{} = &struct{ X int }{1}

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