Go字典使用详解

	// A header for a Go map.
	type hmap struct {
	   // Note: the format of the hmap is also encoded in cmd/compile/internal/gc/reflect.go.
	   // Make sure this stays in sync with the compiler's definition.
	   count     int // # live cells == size of map.  Must be first (used by len() builtin)
	   flags     uint8
	   B         uint8  // log_2 of # of buckets (can hold up to loadFactor * 2^B items)
	   noverflow uint16 // approximate number of overflow buckets; see incrnoverflow for details
	   hash0     uint32 // hash seed
	   buckets    unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.
	   oldbuckets unsafe.Pointer // previous bucket array of half the size, non-nil only when growing
	   nevacuate  uintptr        // progress counter for evacuation (buckets less than this have been evacuated)
	   extra *mapextra // optional fields
	}

// 声明字典 是个 nil 未初始化，直接存值会报错
var s0 map[string] int
// 声明字典并初始化
s1 := map[string]int{}    
// 使用 make 声明
s2 := make(map[string] int)
fmt.Println(s0, s1, s2, s3)

var s4 = map[interface{}]int{
	"1":      1,
	[]int{2}: 2,
	3:        3,
}
fmt.Println(s4)

//初始化
s0 := map[string]int{}
fmt.Println(s0)
//添加key-value
s0["one"] = 1
s0["two"] = 2
fmt.Println(s0)
//修改指定key的值
s0["one"] = 11
s0["two"] = 22
fmt.Println(s0)
//删除指定key的元素
delete(s0, "one")
fmt.Println(s0)
//获取key-value对个数
fmt.Println(len(s0))

s0 := map[string]struct {
	x int
}{}
s0["one"] = struct{ x int }{1}
s0["two"] = struct{ x int }{2}
s0["one"].x = 1 //这里编译器会直接报错

s0 := map[string]struct {
	x int
}{}
s0["one"] = struct{ x int }{1}
s0["two"] = struct{ x int }{2}
s0["one"].x = 1 //这里编译器会直接报错
// 正确做法一
s1 := s0["one"]
s1.x = 111
s0["one"] = s1 
fmt.Println(s0)

// 正确做法二 
// value 的类型是指针类型，指针指向结构体
s0 := map[string]*struct {
	x int
}{}
//创建一个结构体并把指针添加到字典中
s0["one"] = &struct{ x int }{1}
fmt.Println(*s0["one"])
s0["one"].x = 111
fmt.Println(*s0["one"])

s0 := map[string]int{}
s0["one"] = 1
s0["two"] = 2
//接收 key 和 value
for k, vla := range s0 {
	fmt.Printf("%s:%d\n", k, vla)
}
fmt.Println("-----分割线---------------")
//只接收key
for k := range s0 {
	fmt.Printf("%s:%d\n", k, s0[k])
}