为什么在for循环的函数结尾处缺少返回值

Question

The code looks like:

func Contain(livesJSON []LiveJSON, single db.Live) bool {
    for _, json := range livesJSON {
        if json.Start == single.Time && json.Team == single.HomeTeamId {
            return false
        } else {
            return true
        }
    }
}

I have return in both if and else.

Answer 1

There is no guarantee the loop body will be executed. This is the case if you pass nil or an empty slice for livesJSON. That way you would not return anything.

For that case, you must insert a return statement after the loop:

func Contain(livesJSON []LiveJSON, single db.Live) bool {
    for _, json := range livesJSON {
        if json.Start == single.Time && json.Team == single.HomeTeamId {
            return false
        } else {
            return true
        }
    }
    return false
}