golang generic polymorphic (methods, interfaces and AnonymousField)

method

func (s *Struct1)funcName(a,b int) (string，int) {
    ...
}

• Method one more function than the recipient

  • The method of acting on a structure or create their own type
    • Similar in c ++ member function

• Method statement and the user can not a file, but in a package

• Two types of receivers: the pointer value receiver and the receiver

  • Use value type recipient defined method, when invoked, in fact, used copy of the value , so the value of any operation, will not affect the original variables
  • If you want to make changes to the method of the recipient, then it should be used as a pointer to the recipient, using a pointer to a copy of the
  • It is analogous to the first parameter recevier method
  • When in use, value or pointer can be called directly, according to the statement automatically take the address or dereference

• String Methods

  • The print function will automatically call its String method when printing custom data types
  • func (t T) String() string

interface

• If a certain type implements an interface all methods, all places that use this interface, can support the value of this type of
• Do not use a pointer to an interface type, because the interface itself is already a pointer
• When you call the interface called after the jump dynamic computing will lead to failure of CPU cache and branch prediction fails
• Interface variable initialization makes sense, default is nil
• Air interface may be implemented in any type of
  • type empty interface{}
  • Therefore, the use of air interfaces can be implemented generic
• The compiler could check the interface is assigned a set of methods both comparison rather than specific interface type name,
  • If the method A set is a superset of the interface B, the interface variable A can be assigned directly to B
• Implementation of the underlying interface variables
  • Value of the interface is a data structure of a word length
  • The first word contains a pointer to the internal structure of the table, the method sets this internal list memory interface types, examples of the type of binding and the associated
  • The second word contains a pointer to a stored entity type value

• Type assertion

  • grammar:i.(TypeName)
    • i must interface variable
  • If TypeName is the specific type, for the determination of the binding instance whether the type of the interface that the particular type
  • If TypeName is the type of excuse, it will determine whether binding instance of the interface simultaneously implements this interface type

  type Element interface{
  	io.Reader
  }
  // element必须为借口类型
  var element Element = 1
  
  if value,ok := element.(int); ok {
      ...
  } 
  
  if iface, ok := element.(io.Reader); ok {
  	...
  }
  

• The type of query

  • It will be very useful in processing, unknown data type from the outside, such as parsing data such as JSON or XML-encoded
  • grammar:switch v := i.(type){}
    • i must interface variable
    • If i is not bound in any instance, then v is nil
  • Later case either with the particular type, with an interface type may be
  • You can not use fallthrough

    switch v := i.(type) {
    case nil:
    	...
    case string:
        ...
    }

	switch v:= i.(type) {
	case io.Reader, io.Writer:
		...
	}

• The method set
  • The method set value type variable value contains only the recipient declaration method
  • Methods set contains a pointer type variable and pointer values ​​of the recipient declaration

// 指针声明的方法
func(u *User) notify() {
	...
}

type notifier interface {
	notify()
}

func sendNotify(n notifier) {
	n.notify
}

var u User
// 下面的函数编译不通过
// 因为User类型只实现了指针方法集，不能传入值
sendNotify(n)
// 下面的函数通过
sendNotify(&n)
// 上面这样规定的原因是编译器不是总能自动获得一个值得地址，例如这个值是一个常数25
、、

• Do not allow empty interface slice as an argument

  • GitHub
  • CSDN

• When the parameter is the interface, how to use for range

  • Stack Overflow

• Determining whether a slice contains an element

  • Stack Overflow
  • If it is a string slice, you can use an alternative map, but if it is a custom configuration sections, not using map
    • Stack Overflow

• Interface type function

  • Interface type function

• Decoupling dependency injection through the interface

  • Dependency Injection

Anonymous field

• Only the structure type name without a field variable name
• Whereupon the internal structure inherits the fields and methods of inline anonymous field
  • This can simulate inheritance
  • Types of methods can be called directly inside: outer.innerfunc()
  • If the internal type implements an interface, the external type is also automatically
• If there are ways of external and internal types of the same name type, it will cover the internal method
  • At this time if you are calling internal method, it is necessary to explicitly accessed by accessing the internal type
  • outer.inner.func()
• From an existing non-interface when creating a new type of type, is not inherited by the original method
  • If you need to use the original type of method, the original type can be embedded into your new struct defined in the form of an anonymous field

// myMutex没有Lock()方法
type myMutex sync.Mutex
// myMutex有Lock()方法
type myLocker struct {
    sync.Mutex
}