The difference between methods and functions

What is the method? How to use it?

Methods: Apply to the specified data type, that is, bind to the specified data type, so custom types can have methods, not just structs

Use of methods:

Func (A A) test(){fmt.println (a.num)}Copy the code

Method call procedure and parameter passing mechanism

The difference between method and function parameters:

Similarity: When a method is called from a variable, it is called by the same mechanism as a function

Difference: When a variable calls a method, the variable itself is passed to the method as an argument (copied if the variable is of value type, copied if it is of reference type).

Method considerations

1. If a structure type is a value type, it is copied in a method call, following the pass-value mechanism.

2. If you want to change the value of a variable in a method, you can do so by changing the pointer to the structure (more efficiently).

3. Methods in Golang work on the specified data class (bound to the specified data type), so custom types can have methods, not just structs such as int, Float32, etc

   type integer int
   ​
   func (i integer) print(){
       fmt.Println("i=",i)
   }
   ​
   func main(){
       var i integer = 10
       i.print()
   }
   Copy the code

4. Methods use the same rules for access control scope as functions: methods start with a lowercase letter and can only be accessed within this package, and methods start with an uppercase letter and can be accessed within this package and other packages

5. If a type implements the String() method, fmt.println calls the String() output of that variable by default

The difference between methods and functions

1. Different invocation methods

   How a function is called: function name (argument list)

   Method invocation: variable. Method name (argument list)

2. For normal functions, data of a pointer type cannot be passed directly when the receiver is a value type: value types can only be passed value types, and pointer types can only be passed pointer types

3. For methods, when the receiver is of a magnitude type, the method can be called directly using a variable of pointer type, and vice versa