dpgbh20688 2014-08-13 07:20
浏览 19
已采纳

为什么地图不返回其值?

I have a function which simply returns the value of a map. However for some reasons it doesn't do that. Any idea why ? I've pasted here the code. You may also play it using

Try it!

package main

import "fmt"

func main() {    
    a := CountryCode("Australia")    
    fmt.Println(a)    
}

func CountryCode(s string) string {    
    m := make(map[string]string)
    // [snip]
    m["AU"] = "Australia"
    // [snip]
    return m[s]
}

func CodeByCountry(s string) string {
    m := make(map[string]string)
    // [snip]
    m["Australia"] = "AU"
    // [snip]
    return m[s]
}
  • 写回答

1条回答 默认 最新

  • douchi8503 2014-08-13 07:22
    关注

    You're not using the right function, the one using the map whose key is a name. You probably want

    a := CodeByCountry("Australia")
    

    This works.

    But it makes no sense to create the map each time you need it. Take the map creation out of the functions, and put it for example in the init :

    package main
    
    import "fmt"
    
    var byCode = make(map[string]string)
    var byName = make(map[string]string)
    
    func init() {
        m := byCode
        m["AF"] = "Afghanistan"
        m["AL"] = "Albania"
        m["DZ"] = "Algeria"
        m["AS"] = "American Samoa"
    
        m = byName
        m["Austria"] = "AT"
        m["Mozambique"] = "MZ"
        m["Solomon Islands"] = "SB"
        m["United States"] = "US"
        m["Anguilla"] = "AI"
        m["Australia"] = "AU"
    }
    
    func CountryCode(s string) string {
        return byCode[s]
    }
    
    func CodeByCountry(s string) string {
        return byName[s]
    }
    
    func main() {
        a := CodeByCountry("Australia")
        fmt.Println(a)
    }
    

    Another solution for the initialization, as it seems bijective, would be to have one function adding a pair and filling both maps :

    func addInMaps(code,name string) {
         byCode[code] = name
         byName[name] = code
    }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

    报告相同问题?

    悬赏问题

    • ¥20 C语言字符串不区分大小写字典排序相关问题
    • ¥15 关于#python#的问题:我希望通过逆向技术爬取1688搜索页下滑加载的数据
    • ¥15 学习C++过程中遇到的问题
    • ¥15 关于Linux的终端里,模拟实现一个带口令保护的屏保程序遇到的输入输出的问题!(语言-c语言)
    • ¥15 学习C++过程中遇到的问题
    • ¥15 请问,这个嵌入式Linux系统怎么分析,crc检验区域在哪
    • ¥15 二分类改为多分类问题
    • ¥15 Unity微信小游戏上调用ReadPixels()方法报错
    • ¥15 如何通过求后验分布求得样本中属于两种物种其中一种的概率?
    • ¥15 q从常量变成sin函数,怎么改写python代码?