dongmeiba6151
dongmeiba6151
2016-12-21 15:42

有没有惯用的打印字符串指针内容的方法或为nil?

I have a string pointer that may or may not be nil, and I want to print out either the contents of the string if contents exist, or indicate that the pointer is nil if it is nil. Is there a clever way to do this that doesn't involve either an if check or a temporary variable (preferably a single line)?

Right now I'm using something like this:

if p == nil {
    fmt.Print(p)
} else {
    fmt.Print(*p)
}

But this is particularly awkward and verbose when there is other formatting and other variables that are intended to be printed before and/or after that value.

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1条回答

  • douxiangui5011 douxiangui5011 5年前

    You could do something like this:

    func main() {
        var hello SmartString = "hello"
    
        p := &hello
        p.Print()
        p = nil
        p.Print()
    
    }
    
    type SmartString string
    
    func (p *SmartString) Print() {
        if p == nil {
            fmt.Println(p)
        } else {
            fmt.Println(*p)
        }
    }
    

    Whether it's a good idea or not is up to you.

    You can even use the String interface to make it work with fmt.Println

    func main() {
        var hello SmartString = "hello"
    
        p := &hello
        fmt.Println(p)
        p = nil
        fmt.Println(p)
    
    }
    
    type SmartString string
    
    func (p *SmartString) String() string {
        if p == nil {
            return "<nil>"
        }
        return string(*p)
    }
    
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