1

Go有自动生存功能吗?

正如@JimB 正确注意到的那样,我的定义并不那么严格。关于我的目标:在 Python 中,我们有一个非常优雅的“仿真”来实现自动激活:

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

Go有类似的解决方案吗?

4

2 回答 2

3

如果键不存在,Go maps 将返回该类型的零值,或者 map 是nil

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映射将返回0丢失的条目,因此 Go 允许您对不存在的键使用递增和递减运算符:

counters := map[string]int{}
counters["one"]++
于 2016-12-30T16:41:16.920 回答
1

map还扩展了 JimB 的答案,结合interface{}type assertion,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上试试):

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
于 2016-12-30T20:43:40.040 回答