Golang Pit Set

This is a creation in Article, where the information may have evolved or changed.

Func Main () {x: = 1defer func (a int) {FMT. Println ("A=", a)} (x) defer func () {fmt. Println ("x=", X)} () x + +}

Results: x=2 a=1

Note: The required parameters of the defer call are computed when the defer statement executes (copy pass), inside the closure is a reference, defer execution order FIFO

Arrays and Slice

An array is a value type slice is a reference type,

Array creation arr:=[...] int{1,2,3} arr:=[3]int{} arr:=new ([10]int) (Note that new returns a pointer class of [10]int])

Slice creation slice:=[]int{1,2,3} Slice:=arr[n:m] (n <= x < m) Slice:=make ([]int,len,[cap]) (Cap Default=len)

Each slice points to an underlying array, and updates to the slice are reflected on the underlying array, cap=slice the start_index of the array to the array End_index

Reslice Slice1:=slice2[n:m] If n,m exceeds the cap when slice is reslice, it will not cause redistribution of the underlying array, but will panic:runtime error:index out of range

Append (s1,1,2,3) can raise the underlying array redistribution by adding a cap

Copy (DST,SRC) len=min (Len (DST), Len (SRC))

Map

D: = map[*int]struct{x, y float64} {&10: {1.0, 2.0}}

struct and array are also value types

Type s1 struct {s2 struct {a int}}func main () {m: = map[int]struct{a int}{1: {1}}//correct FMT. Println (m) S: = s1{{1}}//exception missing type in composite literalfmt. Println (s)}

The anonymous struct can be used as the value of the map and is easy to assign, while the anonymous struct as a member of the struct requires the name of the struct when it is initialized, and the member variable anonymous struct is inconvenient.

struct Copy copy

U: = user{, "Tom"}var u2 *user = new (User) *U2 = u

Anonymous members (combination better than inheritance)

Type D1 struct {x int}type Data struct {d1x int}func main () {d: = data{d1{10}, 20}d.x = 200d. d1.x = 100fmt. Println (d)}

Interface type inference

If O,ok:=i. (User); ok{     o.xxx}switch o:=i. (type) {case    User:          xxx Case man    :          xxx}

Value copy behavior occurs when an object is assigned to an interface variable

U: = user{1, "Tom"}i: = Tester (U)//cast assignment occurs with copy action//in Golang to be sure that this assignment is a copy action, and that if the Copy object is a pointer, the performance will be better. ID = 100//Explicit modification of the original object U. Name = "Jack" FMT. Println (U, i)//Although the replicas in the ⼝ mouth are not affected