The difference between golang make and new

make, new operation

make is used for memory allocation of built-in types (map, slice and channel) . new is used for various types of memory allocation. (Recommended learning: go)

The built-in function new essentially has the same function as the function of the same name in other languages: new(T) is assigned zero value filling The memory space of type T and returns its address, which is a value of type *T.

In Go terms, it returns a pointer to a newly allocated zero value of type T. One thing is very important:

new返回指针。

The built-in function make(T, args) has different functions from new(T). make can only create slice, map and channel, and return a Type T with initial (non-zero) value, not *T. Essentially, the reason why these three types are different is that references to data structures must be initialized before use.

For example, a slice is a three-item descriptor containing a pointer to the data (internal array), length, and capacity; the slice is nil before these items are initialized. For slices, maps, and channels, make initializes the internal data structures and fills them with appropriate values.

make返回初始化后的（非零）值。

Code example:

var map1 map[string]string = make(map[string]string)
    fmt.Println(map1)
    fmt.Println(map1 == nil)

    var map2 *map[string]string = new(map[string]string)
    fmt.Println(map2)
    fmt.Println(map2 == nil)
    fmt.Println(*map2)
    fmt.Println(*map2 == nil)
    //    var map1 map[string]string
    map1["aaa"] = "AAA"
    map1["bbb"] = "BBB"
    map1["ccc"] = "CCC"
    fmt.Println(map1)
    fmt.Println(len(map1))

Output:

map[]
false
&map[]
false
map[]
true
map[bbb:BBB ccc:CCC aaa:AAA]
Success: process exited with code 0.

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