07-Map声明、元素访问及遍历

Map声明

m := map[string]int{"one": 1, "two": 2, "three": 3}

m1 := map[string]int{}

m1["one"] = 1

m2 := make(map[string]int, 10) // 10 is initial capactity

Map元素的访问

在访问的Key不存在时，Map仍然会返回零值，不能通过nil来判断元素是否存在

func TestAccessNotExistingKey(t *testing.T) {
    m1 := map[int]int{}
    t.Log(m1[1])
    m1[2] = 0
    t.Log(m1[2])
    if v, ok := m1[3]; ok {
            t.Logf("Key 3' value is %d\n", v)
    } else {
            t.Log("Key 3 is not exitsting.")
    }
}

Map遍历

func TestTravelMap(t *testing.T) {
    m1 := map[int]int{1: 1, 2: 4, 3: 9}
    for key, value := range m1 {
            t.Logf("key = %d  value = %d\n", key, value)
    }
}