Swift学习之路-字典的定义与使用

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相比较OC的字典有可变与不可变等的区分，既NSDictionary和NSMutableDictionary
而Swift也有可变和不可变字典，用let和var来区别

定义字典

iOS 中字典是由key和value组成的,字典允许按照某个键来访问元素。key集合不能重复，但是value集合是可重复的

定义一个不可变字典

//方法一
let dicA = ["a":12,"b":13]
print(dicA)
//方法二
//如果key-value 的数据类型不一致用以下方法
let dict = ["name":"张","age":18] as [String : Any]
print(dict)

上面定义字典省略了Dictionary<String,Int>

    //方法三
let dict:Dictionary<String,Int> = ["a":12,"b":14];
    print(dict)

定义一个可变的字典

var dic:Dictionary<String,Any> = ["name":"张三","age":14]
    print(dic)

往字典里面增加一个元素

print("-------新增")
dic["title"] = "大哥"
print(dic)

字典里面修改一个元素

print("-------修改")
dic["name"] = "李四"
print(dic)

字典里面删除一个元素

print("-------删除")
//方法一
//找到元素所在的位置
if let index = dic.index(forKey: "age") {
//删除这个位置对应的元素
    let olditem = dic.remove(at: index)
}
print(dic)
//方法二
dic.removeValue(forKey: "age")

遍历字典

let dic:Dictionary<String,Any> = ["name":"张三","age":14,"title":"老板"]
 //遍历元组 let e: (key: String, value: Any)
 for e in dic {
     print("\(e.key) \(e.value)")
 }
 方法二
 print("-------同时遍历key和value")
 for (kkk,vvv) in dic {
     print("\(kkk) \(vvv)")
 }
 //enumerated() 枚举
 print("-------同时遍历key和value和索引")
 for (kkk,vvv) in dic.enumerated() {
     print("\(kkk) \(vvv)")
 }

合并字典

var dic:Dictionary<String,Any> = ["name":"张三","age":14,"title":"老板"]
let dict:Dictionary<String,Any> = ["name":"大瓜","height":1.9]
for dd in dict {
    dic[dd.key] = dict[dd.key]
}
print(dic)