使用指针定义golang结构函数

发布时间：2020-12-16 19:20:04 所属栏目：大数据来源：网络整理

导读：有人向我解释为什么附加到数组的工作原理： func (s *Sample) Append(name string) { d := Stuff{ name: name,} s.data = append(s.data,d)} Full code here 但不是当你这样做： func (s Sample) Append(name string) { d := Stuff{ name: name,d)} 有什么理

有人向我解释为什么附加到数组的工作原理：

func (s *Sample) Append(name string) {
    d := &Stuff{
        name: name,}
    s.data = append(s.data,d)
}

Full code here

但不是当你这样做：

func (s Sample) Append(name string) {
    d := &Stuff{
        name: name,d)
}

有什么理由为什么要使用第二个例子。

如 in the FAQ所述

我应该定义值或指针的方法吗？

func (s *MyStruct) pointerMethod() { } // method on pointer
func (s MyStruct)  valueMethod()   { } // method on value

First,and most important,does the method need to modify the receiver? If it does,the receiver must be a pointer. (Slices and maps act as references,so their story is a little more subtle,but for instance to change the length of a slice in a method the receiver must still be a pointer.)

In the examples above,if pointerMethod modifies the fields of s,the caller will see those changes,but valueMethod is called with a copy of the caller’s argument (that’s the definition of passing a value),so changes it makes will be invisible to the caller.

在你的情况下，func(s Sample)Append(name string)修改一个副本。

laher提醒我们in the comments使用一个值而不是指针也意味着获取一个副本，并尊重对象的不变性::

You’d want to use the non-pointer valueMethod when (for nstance) you’re returning a [value derived from an] ‘immutable’ private property.

参见“Why are receivers pass by value in Go?”：

Can be useful if for instance you have a small immutable object. The caller can know for certain that this method doesn’t modify it’s receiver. They can’t know this if the receiver is a pointer without reading the code first.

（编辑：李大同）

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