在Go中使用重复的函数调用进行循环

Question

I'm looping over state changes where the change & condition are defined in a function and was hoping to write a for statement where I only declare the function call once.

This code works, but repeating message, flag = a.foo() feels messy. Is there a more effective way to write a for loop when the initial statement is the same as the post statement?

func (a *Example) foo() (string, bool) {
    // Function affects state of a
    // returns message on each step and flag if condition reached
}

func main() {
    // Step through each state change until flag is triggered
    for message, flag := a.foo(); flag; message, flag = a.foo() {
        fmt.Printf("%s
", message)
    }
}

I was hoping that there would be some kind of equivalent to how nicely it fits in to an if statement like this:

if message, flag := a.foo(); !flag {
    fmt.Printf("%s
", message)
}

---

In fact, I was rather hoping I could just change that if to a for but, alas, expected ';'. found '{'

I may well be asking too much, but if there is an answer I'd love to hear it. Thanks

Answer 1

As far as I know there is no way to do exactly what you want (though I'd love if it was possible too). You could use an "infinite" loop and write the break condition manually, although that also isn't too great, something like:

func main() {
    for {
        msg, flag := a.foo()
        if flag {
            break
        }
        fmt.Printf(...)
    }
}