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关于Golang struct{}{}用法和注意事项

 2 years ago
source link: https://studygolang.com/articles/35190
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关于Golang struct{}{}用法和注意事项

ljq · 2天之前 · 271 次点击 · 预计阅读时间 1 分钟 · 大约8小时之前 开始浏览    

引自ljq@GitHub

  • struct {} struct {}是一个无元素的结构体类型，通常在没有信息存储时使用。 优点：不需要内存来存储struct{}类型的值。
  • struct{}{} struct{}{}是一个复合字面量，它构造了一个struct{}类型的值，该值也是空。
  • 两个structt{}{}地址相等
package main

import "fmt"

type idBval struct {
    Id int
}

func main() {
    idA := struct{}{}
    fmt.Printf("idA: %T and %v \n\n", idA, idA)

    idB := idBval{
        1,
    }
    idB.Id = 2
    fmt.Printf("idB: %T and %v \n\n", idB, idB)

    idC := struct {
        Id int
    }{
        1,
    }
    fmt.Printf("idC: %T and %v \n\n", idC, idC)

    mapD := make(map[string]struct{})
    mapD["mapD"] = struct{}{}
    _, ok := mapD["mapD"]
    fmt.Printf("mapD['mapD'] is %v \n\n", ok)

    sliceE := make([]interface{}, 2)
    sliceE[0] = 1
    sliceE[1] = struct{}{}
    fmt.Printf("idE: %T and %v \n\n", sliceE, sliceE)

}

Output：


idA: struct {} and {} 

idB: main.idBval and {2} 

idC: struct { Id int } and {1} 

mapD['mapD'] is true 

idE: []interface {} and [1 {}]

引自ljq@GitHub


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