dougaxing8673 2017-10-13 09:34
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如何在golang中返回int或nil?

I'm a java developer and I am learning Go. I'm writing simple 'pop' operation for a LIFO stack. The question is with the return value when there are no values in the stack. In java, I'm able to return a wrapper(Integer) in the positive case and null when there are no values. It's natural from my perspective.

How can I do something similar in Go? Are there any struct wrappers for primitives? Do I need to return two values(the second will indicate error code)? Or do I need to throw an exception?

Here's how it looks for now:

func (s *stack) Pop() (int, bool)  {
    if s.size == 0 {
        return 0, true
    }
    s.size--
    val := s.stack[s.size]
    return val, false
}

Is it good style?

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  • douguio0185 2017-10-13 09:43
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    Since a number can't be nil, you can't return nil for integer, unless you define the return value as a pointer. The idiomatic solution in Go is by defining your method to return more than one values, e.g.

    func (s *stack) Pop() (int, bool) {
        //does not exists
        if ... {
            return 0, false
        }
    
        //...
    
        //v is the integer value
        return v, true
    }
    

    Then somewhere you can call Pop as

    s := &stack{}
    if v, ok := s.Pop(); ok {
        //the value exists
    }
    

    Take a look at comma, ok idiom.

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