Question

正如@JimB正确地注意到的那样，我的定义并不严格。关于我的目标：在Python中，我们有一个非常优雅的“模拟”用于自动化：

class Path(dict):
    def __missing__(self, key):
            value = self[key] = type(self)()
            return value

Go有类似的解决方案吗？

Answer 1

如果密钥不存在，或者地图为nil

，Go地图将为该类型返回零值

https://play.golang.org/p/sBEiXGfC1c

var sliceMap map[string][]string

// slice is a nil []string
slice := sliceMap["does not exist"]


var stringMap map[string]string

// s is an empty string
s := stringMap["does not exist"]

由于带有数值返回的地图将返回0以查找缺失的条目，因此Go允许您在不存在的键上使用递增和递减运算符：

counters := map[string]int{}
counters["one"]++

Answer 2

同样通过map，interface{}和type assertion的组合扩展JimB的答案，您可以动态创建任何复杂的结构：

type Obj map[interface{}]interface{}

func main() {
    var o Obj

    o = Obj{
        "Name": "Bob",
        "Age":  23,
        3:      3.14,
    }
    fmt.Printf("%+v\n", o)

    o["Address"] = Obj{"Country": "USA", "State": "Ohio"}
    fmt.Printf("%+v\n", o)

    o["Address"].(Obj)["City"] = "Columbus"
    fmt.Printf("%+v\n", o)

    fmt.Printf("City = %v\n", o["Address"].(Obj)["City"])
}

输出（在Go Playground上尝试）：

map[Name:Bob Age:23 3:3.14]
map[Age:23 3:3.14 Address:map[Country:USA State:Ohio] Name:Bob]
map[3:3.14 Address:map[Country:USA State:Ohio City:Columbus] Name:Bob Age:23]
City = Columbus

Go有自动化吗？

2 个答案: