Go语言内建方法之append && delete && copy

• 用来操作变量

• slice -> append(添加一个元素)

     package main
     import "fmt"
     func main() {
         appendElementSlice()
     }
     func appendElementSlice()  {
          mIDSlice := make([]string, 2)  //要求较高的时候我们需要声明定长(避免操作内存),append会操作内存
          mIDSlice[0] = "id-1"
          mIDSlice[1] = "id-2"
          fmt.Println("追加前的cap(容量)=",cap(mIDSlice)) //追加前的cap(容量)= 2
          fmt.Print("\n")
          mIDSlice = append(mIDSlice,"id-3")  //追加一个元素,扩容
          fmt.Println(mIDSlice)  //[id-1 id-2 id-3]
          fmt.Print("\n")
          fmt.Println("len:",len(mIDSlice)) //len: 3
          fmt.Print("\n")
          fmt.Println("追加后的cap(容量)=",cap(mIDSlice)) //追加后的cap(容量)= 4
     }

• slice -> copy(复制整个切片,有一定规则)

     package main
     import "fmt"
     func main() {
         copyForSlice()
     } 
     func copyForSlice()  {
         mIDSliceDst := make([]string, 3)
         mIDSliceDst[0] = "id-dst-1"
         mIDSliceDst[1] = "id-dst-2"
         mIDSliceDst[2] = "id-dst-3"
     
         mIDSliceSrc := make([]string, 2)
         mIDSliceSrc[0] = "id-src-1"
         mIDSliceSrc[1] = "id-src-2"
     
         //目标源的长度大于被copy源的长度时取被copy源的长度的值替换相同key的value值
         //目标源的长度小于被copy源的长度时取目标源的长度的值替换相同key的value值
         copy(mIDSliceDst, mIDSliceSrc)
     
         fmt.Println(mIDSliceDst)    //[id-src-1 id-src-2 id-dst-3]
     }

• map -> delete (删除)

    package main
    
    import "fmt"
    
    func main() {
        deleteFormMap()
    }
    //删除map中的数据
    func deleteFormMap()  {
        mIDMap := make(map[int]string)
        mIDMap[0] = "id-1"
        mIDMap[1] = "id-2"
        mIDMap[2] = "id-3"
        fmt.Println(mIDMap)            //map[0:id-1 1:id-2 2:id-3]
        fmt.Print("\n")
        delete(mIDMap, 0)              //删除指定下标的值
        fmt.Println(mIDMap)            //map[1:id-2 2:id-3]
    }