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| 1 | +package main |
| 2 | + |
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + "reflect" |
| 6 | +) |
| 7 | + |
| 8 | +// import ( |
| 9 | +// "fmt" |
| 10 | +// ) go_basic_courses |
| 11 | + |
| 12 | +func main() { |
| 13 | + // 声明一个集合字典,默认为空 |
| 14 | + a := 15 |
| 15 | + fmt.Println("address of b is ", a) |
| 16 | + fmt.Println("address of b is ", &a) |
| 17 | + m := map[string]int{} |
| 18 | + fmt.Println("address of b i is ", m) |
| 19 | + fmt.Printf("Type of a is %T\n", m) |
| 20 | + fmt.Printf("m值是 %v \n", m == nil) |
| 21 | + var dir map[string]string |
| 22 | + fmt.Printf("dir字典的值是: | %v \n", dir) |
| 23 | + fmt.Printf("dir字典是否为nil | %v \n", dir == nil) |
| 24 | + // nil map不能赋值,如果直接赋值会报错:"panic: assignment to entry in nil map",下面语句将会报错 |
| 25 | + // dir["name"] = "Tinywan" |
| 26 | + |
| 27 | + fmt.Println("----------------------------") |
| 28 | + // 使用make函数进行初始化创建一个非nil的map |
| 29 | + dir = make(map[string]string) |
| 30 | + // map是引用类型,未初始化的是指向nil,初始化了以后应该就有自己的内存空间了,所以不是nil |
| 31 | + fmt.Printf("dir字典的值是: | %v \n", dir) |
| 32 | + fmt.Printf("dir字典是否为nil | %v \n", dir == nil) |
| 33 | + |
| 34 | + fmt.Println("----------------------------") |
| 35 | + // make之后分配内存了,一旦分配了内存地址就不为空了,可以赋值了 |
| 36 | + dir["name"] = "Tinywan" |
| 37 | + fmt.Printf("dir字典的键:值 |%v \n", dir) |
| 38 | + fmt.Printf("dir字典的类型 |%v \n", reflect.TypeOf(dir)) |
| 39 | + fmt.Printf("name的值是 |%v \n", dir["name"]) |
| 40 | + // value, ok := s["ok"] |
| 41 | + // if ok == nil { |
| 42 | + // s := make(map[string]int) |
| 43 | + // s["ok"] = 19 |
| 44 | + // fmt.Println(s["ok"]) |
| 45 | + // } |
| 46 | + // fmt.Println(s["ok"]) |
| 47 | +} |
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