Go语言内建方法之append、delete 、copy (十四)

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)

代码语言：javascript复制

   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)

代码语言：javascript复制

   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)

代码语言：javascript复制

  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]
  }

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