Swift 集合类型之字典

创建空字典

import UIKit

// 创建空字典
var namesOfIntegers = [Int : String]()

// 插入值
namesOfIntegers[16] = "sixteen"

namesOfIntegers = [:]

创建有初始值的字典

// 创建有初始值的字典
var airports : [String : String] = ["YYZ" : "Toronto Pearson", "DUB" : "Dublin"]

print("The airports dictionary contains \(airports.count) items")

if airports.isEmpty {
    print("The airports dictionary is empty.")
} else {
    print("The ariports dictionray is not empty")
}

插入新键值对

// 插入新键值对
airports["LHR"] = "London"
print(airports)

console log 如下

字典插入新键值对.png

修改

// 修改
airports["LHR"] = "London Heathrow"
print(airports)

if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {
    print("The old value for DUB was \(oldValue)")
}

print(airports)

console log 如下

修改字典.png

访问

// 访问
if let airportName = airports["DUB"] {
    print("The name of the airport is \(airportName)")
} else {
    print("That airport is not in the airports dictionary")
}

console log 如下

访问字典键.png

移除键对应的值

// 移除
airports["APL"] = "Apple International"
print(airports)
airports["APL"] = nil
print(airports)

if let removedValue = airports.removeValueForKey("DUB") {
    print("The removed airport's name is \(removedValue)")
} else {
    print("The airports dictionary does not contain a value for DUB.")
}
print(airports)

console log 如下

移除键对应的值.png

遍历

// 遍历
for (airportCode, airportName) in airports {
    print("\(airportCode) : \(airportName)")
}

for airportCode in airports.keys {
    print("Airport code :\(airportCode)")
}

for airportName in airports.values {
    print("Airport name :\(airportName)")
}

let airportCodes = [String](airports.keys)
print(airportCodes)

let airportNames = [String](airports.values)
print(airportNames)

console log 如下

遍历字典.png