dousi1994 2014-07-27 19:13
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golang 1个字段的2个切片类型

In light of the fact that golang does not support unions, what is the best way to achieve:

type foo struct {
    words []string
    nums []int
}

such that only words or nums can be used at once. One thing I've tried is:

type foo struct {
    values []interface{}
}

but I prefer something that restricts the types to the two mentioned or something with pointers.

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  • douyue5856 2014-07-27 20:46
    关注

    Use a foo package to hide the implementation. For example,

    package foo
    
    const (
        typeWords = iota + 1
        typeNums
    )
    
    type Foo struct {
        fooType byte
        words   []string
        nums    []int
    }
    
    func NewWords(words []string) *Foo {
        return &Foo{fooType: typeWords, words: words}
    }
    
    func NewNums(nums []int) *Foo {
        return &Foo{fooType: typeNums, nums: nums}
    }
    
    func (f *Foo) Words() []string {
        if f.fooType != typeWords {
            return nil
        }
        return f.words
    }
    
    func (f *Foo) Nums() []int {
        if f.fooType != typeNums {
            return nil
        }
        return f.nums
    }
    

    ADDENDUM:

    Since we are hiding the implementation of package foo, we can implement it another way. For example, we could adopt twinj's suggestion and use an interface. To ensure some degree of generality, let's add another []string type Phrases. The value types are used to distinguish between the two []string types.

    package foo
    
    type (
        valueWords   []string
        valuePhrases []string
        valueNums    []int
    )
    
    type Foo struct {
        value interface{}
    }
    
    func NewWords(words []string) *Foo {
        return &Foo{value: valueWords(words)}
    }
    
    func (f *Foo) Words() []string {
        value, ok := f.value.(valueWords)
        if !ok {
            return nil
        }
        return value
    }
    
    func NewPhrases(phrases []string) *Foo {
        return &Foo{value: valuePhrases(phrases)}
    }
    
    func (f *Foo) Phrases() []string {
        value, ok := f.value.(valuePhrases)
        if !ok {
            return nil
        }
        return value
    }
    
    func NewNums(nums []int) *Foo {
        return &Foo{value: valueNums(nums)}
    }
    
    func (f *Foo) Nums() []int {
        value, ok := f.value.(valueNums)
        if !ok {
            return nil
        }
        return value
    }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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