Iv. Golang Type Explanation--go language study notes

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

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Mapping map

1. A "key-value" pair
2. Key points: attention to concurrent read and write situation, locked
3. Cannot write to uninitialized map, throws exception (panic)
4. For iterative operations, each result may be inconsistent (disorderly order)

varMMap[string]intm["K1"] =7 //Error: Assignment to entry in nil mapM: = Make(Map[string]int)//Initialize to an empty map: [], can read and writem["K1"] =7m["K2"] = -Delete(M,"K2")//delete the value corresponding to "K2"V, OK: = m["K2"]//Check if the value of "K2" existsFmt. Println (m["K3"])//non-existent key returns null value by default forK, V: =Rangem {//The results of the iteration may be inconsistent each timeFmt. Println (k, V)}

The make () built-in method can only be used to create slice, map, and channel
Slice, map, channel is a reference to the underlying data structure that must be initialized before use.

Pointer

1. Go has pointers, but there is no pointer operation. You cannot traverse the individual bytes of a string with a pointer variable.
2. The Go pointer is just a reference.
3. The FETCH operator & get the variable storage address, can be assigned to a pointer.

To create your own defined type

type Person struc {    string    int    stringnew"Lishi"// 首字母大写字段，可导出，可在其它包中进行读写"28""He"// 首字母小写字段，不可导出，不可在其它包中进行读写

Method definition

funcstring) {    fmt.Println("Study some language...", lang)}p.Study("Golang")

Anonymous fields

typeSstruct{AstringBstring}typeBstruct{S//Anonymous field, only Type S, field name is SBint //Field name is B    int     //Anonymous field, only type int, meaningless}varb BB.S.A ="a" //Assign a value to the anonymous field SB.A ="a"   //Ibid .Fmt. Println (b)//Output result: {{a}}not {a}typeStringstringb.s.b ="B" //Assign a value to the anonymous field SB.B =Ten    //Name conflict, different, cannot assign a value to the same field in an anonymous field

Method inheritance

typestruct {    string}typestruct {    S}func (s *S) String() {    fmt.Println("In A: ", s.a, s.b)}var"a""b"// 等价于 b.S.String()

Method overrides

Add a method to type B to overwrite the String in the type S ()

type S struct {    a, b string}type B struct {    S}func (s *S) String() {    fmt.Println("In A: ", s.a, s.b)}func (b *B) String() {    fmt.Println("In B: ", b.a, b.b)}var b Bb.a"a"b.b"b"b.S.String()b.String() // 不等价于 b.S.String()

byte alignment

struct {    byte    string    byte}unsafe32

Compare

struct {    string    byte    byte}unsafe24