英文:
What is the difference between parameter and receiver
问题
func (p *Page) save() error {
filename := p.Title + ".txt"
return ioutil.WriteFile(filename, p.Body, 0600)
}
英文:
I am following a Go tutorial and am stuck as I cant understand a particular method signature:
func (p *Page) save() error {
filename := p.Title + ".txt"
return ioutil.WriteFile(filename, p.Body, 0600)
}
The docs explain this as follows:
> This method's signature reads: "This is a method named save that takes as its receiver p, a pointer to Page . It takes no parameters, and returns a value of type error."
I cant understand what the receiver is. I would read this as it being a parameter but then I would expect a parameter to be in save().
答案1
得分: 29
接收器只是参数的一种特殊情况。Go语言提供了一种语法糖，通过将第一个参数声明为接收器来将方法附加到类型上。
例如：
func (p *Page) save() error
读作“将一个名为save的方法附加到类型*Page上，并返回一个error”，而不是声明：
func save(p *Page) error
这将读作“声明一个名为save的函数，它接受一个类型为*Page的参数，并返回一个error”。
作为语法糖的证明，您可以尝试以下代码：
p := new(Page)
p.save()
(*Page).save(p)
最后两行表示完全相同的方法调用。
另外，请阅读这个答案。
英文:
The receiver is just a special case of a parameter. Go provides syntactic sugar to attach methods to types by declaring the first parameter as a receiver.
For instance:
func (p *Page) save() error
reads "attach a method called save that returns an error to the type *Page", as opposed to declaring:
func save(p *Page) error
that would read "declare a function called save that takes one parameter of type *Page and returns an error"
As proof that it's only syntactic sugar you can try out the following code:
p := new(Page)
p.save()
(*Page).save(p)
Both last lines represent exactly the same method call.
Also, read this answer.
答案2
得分: 13
接收器是你声明方法的对象。
当想要向一个对象添加方法时，使用这种语法。
例如：http://play.golang.org/p/5n-N_Ov6Xz
英文:
The receiver is the object on what you declare your method.
When want to add a method to an object, you use this syntax.
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