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字典是一种存储相同类型多重数据的存储器。每个值（value）都关联独特的键（key），键作为字典中的这个值数据的标识符。和数组中的数据项不同，字典中的数据项并没有具体顺序。
字典写作Dictionary<Key, Value>。也可以写作[Key: Value]
创建空字典
var namesOfIntegers = [Int: String]()
// namesOfIntegers is an empty [Int: String] dictionary
类型推断写作[:]
namesOfIntegers[16] = "sixteen"
// namesOfIntegers now contains 1 key-value pair
namesOfIntegers = [:]
// namesOfIntegers is once again an empty dictionary of type [Int: String]
创建字典字面量
[key 1: value 1, key 2: value 2, key 3: value 3]
var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]
类型推断写作
var airports = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]
访问和修改
count返回字典的键值对数
isEmpty判断字典是否为空
airports["LHR"] = "London Heathrow
if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {
print("The old value for DUB was \(oldValue).")
}
// Prints "The old value for DUB was Dublin.
removeValueForKey(_:)删除键值对
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.")
}
// Prints "The removed airport‘s name is Dublin Airport.
遍历
for (airportCode, airportName) in airports {
print("\(airportCode): \(airportName)")
}
// YYZ: Toronto Pearson
// LHR: London Heathrow
for airportCode in airports.keys {
print("Airport code: \(airportCode)")
}
// Airport code: YYZ
// Airport code: LHR
for airportName in airports.values {
print("Airport name: \(airportName)")
}
// Airport name: Toronto Pearson
// Airport name: London Heathrow
【Swift学习】Swift编程之旅---集合类型之Dictionaries（八）
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原文地址：http://www.cnblogs.com/salam/p/5401686.html
