go - := 左侧非名称

Question

这个问题已经有答案了:

Go fails to infer type in assignment: "non-name on left side of :=" (4 个回答)

Why is a struct's field a "non-name" [duplicate] (1 个回答)

已关闭 4 年前。

我正在go中练习/尝试一些同步机制。 .

为什么最后一个for迭代无法分配缓冲 channel 保存的值 valchan进入mysl slice ？

错误是

./myprog.go:28:7: non-name mysl[i] on left side of :=

package main

import (
    "sync"
)

const NUM_ROUTINES = 2

func sendValue(c chan string) {
    c <- "HelloWorld"
}

func main() {
    valchan := make(chan string, NUM_ROUTINES)
    var wg sync.WaitGroup
    wg.Add(NUM_ROUTINES)

    for i := 0; i < NUM_ROUTINES; i++ {
        go func() {
            sendValue(valchan)
            wg.Done()
        }()
    }
    wg.Wait()

    mysl := make([]string, 2, 2)
    for i := 0; i < NUM_ROUTINES; i++ {
        mysl[i] := <-valchan
    }
}

Answer 1

您正在使用“短变量声明”语法。来自 language specification :

It is shorthand for a regular variable declaration with initializer expressions but no types

...

Unlike regular variable declarations, a short variable declaration may redeclarevariables provided they were originally declared earlier in the same block (or the parameter lists if the block is the function body) with the same type, and at least one of the non-blank variables is new.

换句话来说:您的代码尝试重新声明 mysl[i]。这不符合“至少一个非空变量是新的”规则，因此编译器会提示。相反，您只想使用 = 运算符进行赋值。