A Tour of Go Mutating Maps

最新推荐文章于 2024-04-17 14:48:42 发布

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最新推荐文章于 2024-04-17 14:48:42 发布

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原文链接：http://www.cnblogs.com/ghgyj/p/4055485.html

本文通过一个Go语言示例展示了如何使用map进行插入、更新、检索和删除元素的操作，并解释了如何检查键是否存在及键不存在时的行为。

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Insert or update an element in map m:

m[key] = elem

Retrieve an element:

elem = m[key]

Delete an element:

delete(m, key)

Test that a key is present with a two-value assignment:

elem, ok = m[key]

If key is in m, ok is true. If not, ok is false and elem is the zero value for the map's element type.

Similarly, when reading from a map if the key is not present the result is the zero value for the map's element type.

package main 
import "fmt"

func main() {
    m := make(map[string]int)

    m["Answer"] = 42
    fmt.Println("The value:", m["Answer"])

    m["Answer"] = 48
    fmt.Println("The value:", m["Answer"])

    v, ok := m["Answer"]
    fmt.Println("The value:", v, "Present?", ok)


    delete(m, "Answer")
    fmt.Println("The value:", m["Answer"])

    v2, ok2 := m["Answer"]
    fmt.Println("The value:", v2, "Present?", ok2)
}