//: Playground - noun: a place where people can play
import UIKit
/*
* 本节内容:
* 1.字典的声明和初始化
* 2.字典的遍历
* 3.字典的增删改查
*/
/*
* 数组: 有序, 可以重复
* 字典: 无序, 不可重复(key)
* 集合: 无序, 不可重复
*/
// 隐式声明字典[key: value]
// 一旦初始化之后, 确定了key和value类型
var counties = ["CN": "People Republic Of China", "UK": "United Kindom", "IN": "India"]
// 显示声明
var countryOne: [String: String] = ["US": "United States"]
// 使用四种方式声明不包含key/value的字典
var emptyDicOne: [Int: String] = [:] //1.
var emptyDicTwo = [Int: String]() //2.
var emptyDicThree: Dictionary<Int, String> = [:] //3.
var emptyDicFour = Dictionary<Int, String>() //4.
// 2和4通过调用init构造创建
// 1和3是显示声明key和value
// 遍历
for key in counties.keys {
print("所有key: \(key)")
}
for value in counties.values {
print("所有value: \(value)")
}
for (key, value) in counties {
print("key: \(key) and value: \(value)")
}
// 查
// countryName是String?
var countryName = counties["CN"]
// countryName可选型
counties.count // 多少组key/value
emptyDicFour.isEmpty
counties.keys
// 值类型(字典)和引用类型
counties == countryOne
// 增: 对不存在的key设置value就是添加
counties["FR"] = "France"
counties
// 改: 对存在的key设置value就是改
counties["UK"] = "Great Britain"
counties.updateValue("Britain", forKey: "UK")
// 删
counties["IN"] = nil
counties
counties.removeValue(forKey: "UK")
counties
Swift 系统学习 10 字典 Dictionary 增删改查
最新推荐文章于 2022-05-06 14:56:28 发布