Golang 中 new 和 make的区别

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参考链接: https://studygolang.com/articles/24026#reply0

Golang 内置两个函数，new 和 make ,其作用都是用来分配内存的。这么说可能会造成混淆，但其实规则很简单，其实他们适用于不同的类型。

make 函数只用于给 slice、map、channel进行初始化；
new 函数参数为一个类型不是一个值，用该类型的零值初始化一块空间，并返回该空间的指针。

我们看一下下面的案例：

package main

import (
    "fmt"
)

func main() {
    var i *int

    *i=10
    fmt.Println(*i)

}

运行报错，panic: runtime error: invalid memory address or nil pointer dereference。错误很明显提示无效的内存地址或者空指针错误。
如何解决呢，很简单，我们只需要使用new来进行内存分配。

package main

import (
    "fmt"
)

func main() {
    var i *int
    i = new(int)
    *i = 10
    fmt.Println(*i)

}
// 再次运行，完美输出结果 10

我们再通过源码看看new 函数

// The new built-in function allocates memory. The first argument is a type,
// not a value, and the value returned is a pointer to a newly
// allocated zero value of that type.
func new(Type) *Type
只接收一个参数（type），并且返回了一个初始化为零值的内存指针。

再看看 make 函数

// The make built-in function allocates and initializes an object of type
// slice, map, or chan (only). Like new, the first argument is a type, not a
// value. Unlike new, make's return type is the same as the type of its
// argument, not a pointer to it. The specification of the result depends on
// the type:
// Slice: The size specifies the length. The capacity of the slice is
// equal to its length. A second integer argument may be provided to
// specify a different capacity; it must be no smaller than the
// length. For example, make([]int, 0, 10) allocates an underlying array
// of size 10 and returns a slice of length 0 and capacity 10 that is
// backed by this underlying array.
// Map: An empty map is allocated with enough space to hold the
// specified number of elements. The size may be omitted, in which case
// a small starting size is allocated.
// Channel: The channel's buffer is initialized with the specified
// buffer capacity. If zero, or the size is omitted, the channel is
// unbuffered.
func make(t Type, size ...IntegerType) Type