英文:
Method receivers
问题
Go方法接收器需要一个类型和一个类型的变量名，例如：
type MyFloat float64
func (x MyFloat) Abs() float64 {
if x < 0 {
return float64(-x)
}
return float64(x)
}
func main() {
f := MyFloat(-math.Sqrt2)
fmt.Println(f.Abs())
}
接收器在方法中使用x作为类型的变量名。为什么要指定x的名称呢？由于我可以在任何MyFloat的实例上调用该方法（不仅仅是命名为x的实例），为什么我还要指定x呢？既然接收器是一个类型或者类型的引用，为什么不像这样只接收类型或者指针：
func (MyFloat) Abs() float64 {
if this < 0 {
return float64(-this)
}
return float64(this)
}
我的假设是，与Java中的this不同，Go允许使用任何名称作为接收器的变量名。是这样吗？
英文:
Go method receivers take a type along with a variable name for the type, example:
type MyFloat float64
func (x MyFloat) Abs() float64 {
if x < 0 {
return float64(-x)
}
return float64(x)
}
func main() {
f := MyFloat(-math.Sqrt2)
fmt.Println(f.Abs())
}
The receiver takes "x" along with the type receiving the method. What is the significance of the name 'x'. Since i am able to invoke the method on any instance of MyFloat ( not just on the one named as x ) why do i have to specify the x ? Since the receiver is a Type or a reference to a type why not simply take the type or the pointer alone like this
func (MyFloat) Abs() float64 {
if this < 0 {
return float64(-this)
}
return float64(this)
}
My assumption is instead of this in Java golang allows any name? Is that so ?
答案1
得分: 3
你的假设是正确的：在方法定义中，接收者必须明确命名。这样可以避免任何歧义。在你的例子中，Go编译器怎么可能猜到x是接收者呢？
请注意，在Go语言中，使用"self"、"this"或"me"作为接收者名称被认为是不好的风格。接收者的名称应该简短，一个字母就足够了。更多信息请参考https://code.google.com/p/go-wiki/wiki/CodeReviewComments#Receiver_Names。
英文:
Your assumption is exact: the receiver has to be explicitly named in a method definition. It avoids any ambiguity. In your example, how could the Go compiler guess that x is the receiver?
Note that using "self" or "this" or "me" as the receiver name is considered as bad style in go. The name should be short - one letter is fine. See more information at https://code.google.com/p/go-wiki/wiki/CodeReviewComments#Receiver_Names
答案2
得分: 1
这是一个设计选择。
Java使用this，Go语言选择了另一种机制。
在Go中，将接收者设为指针或非指针都是合法的。
我们来看一下：
func (t Type) Id() { return t }
func (t *Type) IdPointer() { return t }
如果Go使用Java的设计会怎样呢？
它将变成：
func (Type) Id() { return this }
func (*Type) IdPointer() { return this }
首先，(*Type)是令人困惑的。
其次，this也可以是指针或值。同样令人困惑。
但是，无论如何，你可以像这样设计Go语言。
毕竟这是一个选择。
英文:
It's a design choice.
Java use this, Go-lang choose another mechanic.
In Go, it's legal to make the receiver a pointer or not.
Let's see:
func (t Type) Id() { return t }
func (t *Type) IdPointer() { return t }
What if Go use Java's design?
It will became:
func (Type) Id() { return this }
func (*Type) IdPointer() { return this }
Firstly, it is confused that what (*Type) is.
Secondly, this can also be a pointer or a value. Also confused.
But, anyway, you can design Go-lang like this.
It is a choice after all.
答案3
得分: 0
我认为你没有正确使用，你应该在结构体中使用它。接收器应该引用结构体的字段。
例如：
package main
import "fmt"
type Decimal struct {
first float64
}
func (x Decimal) out() float64 {
return x.first
}
func main() {
var start Decimal
start.first = 10.8
show := start.out()
fmt.Println(show)
}
请注意，这是一个示例代码，用于演示如何在结构体中使用方法。
英文:
I think you are not using correctly you should use it in a struct.Where the receiver makes a reference to the struct's fields.
For example:
package main
import "fmt"
type Decimal struct {
first float64
}
func (x Decimal) out() float64 {
return x.first
}
func main() {
var start Decimal
start.first = 10.8
show := start.out()
fmt.Println(show)
}
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