Swift 字典

Swift字典是一個簡單的容器，可以以無序的方式包含多個鍵值對數據。愛掏網 - it200.com

當您想要在集合中使用某個標識符查找值時，可以使用Swift字典代替數組。愛掏網 - it200.com假設我們要搜索一個國家的首都。愛掏網 - it200.com在這種情況下，我們將創建一個以國家為鍵和首都為值的字典。愛掏網 - it200.com現在，通過使用國家鍵進行搜索，您可以從集合中獲取首都。愛掏網 - it200.com在這里，我們將一個國家與其首都配對。愛掏網 - it200.com

聲明一個空字典

要創建一個空字典，我們在方括號[]中指定鍵:值的數據類型。愛掏網 - it200.com

示例

let emptyDictionary:[Int:String] = [:]
print(emptyDictionary)

或者

let emptyDictionary:Dictionary = [:]
print(emptyDictionary)

輸出：

[:]

聲明一個帶有一些值的字典

let valDictionary = ["a":10, "b":20, "c":30, "d":40, "e":50, "f":60, "g":70, "h":80, "i":90]
print(valDictionary)

輸出:

["c": 30, "d": 40, "g": 70, "b": 20, "a": 10, "f": 60, "h": 80, "i": 90, "e": 50]

在上面的程序中，我們沒有明確聲明類型，但是我們初始化了一些默認元素。愛掏網 - it200.com元素是鍵值對，鍵是字符串類型，值是整數類型。愛掏網 - it200.com 從兩個數組創建字典 我們也可以從數組創建字典。愛掏網 - it200.com 示例：

let customKeys = ["India", "Pakistan", "United Kingdom"]
let customValues = ["New Delhi", "Islamabad", "London"]
let newDictionary = Dictionary(uniqueKeysWithValues: zip(customKeys,customValues))
print(newDictionary)

輸出結果：

["India": "New Delhi", "United Kingdom": "London", "Pakistan": "Islamabad"]

在Swift中訪問字典元素

我們可以通過在字典名稱之后的方括號中包含我們想要訪問的值的鍵來訪問Swift字典的元素。愛掏網 - it200.com

示例

let valDictionary = ["a":10, "b":20, "c":30, "d":40, "e":50, "f":60, "g":70, "h":80, "i":90]
print(valDictionary["c"])
print(valDictionary["f"])

輸出：

Optional(30)
Optional(60)

使用for-in循環在Swift中訪問字典元素

示例

let valDictionary = ["a":10, "b":20, "c":30, "d":40, "e":50, "f":60, "g":70, "h":80, "i":90]
for (key,value) in valDictionary {
    print("key:\(key) value:\(value)")
}

輸出:

key:h value:80
key:d value:40
key:a value:10
key:g value:70
key:e value:50
key:b value:20
key:c value:30
key:f value:60
key:i value:90

在Swift中修改字典元素

我們可以通過使用一個新的鍵作為索引并賦值給一個新的值，在Swift字典中添加一個新的元素。愛掏網 - it200.com

示例

var valDictionary = ["India":"New Delhi", "China":"Beijing", "USA":"Washington D.C."]
valDictionary["Germany"] = "Berlin"
print(valDictionary)

輸出：

["Germany": "Berlin", "China": "Beijing", "USA": "Washington D.C.", "India": "New Delhi"]

更改字典中的元素

示例

var valDictionary = ["India":"New Delhi", "China":"Beijing", "USA":"Washington D.C."]
valDictionary["India"] = "NEW DELHI"
print(valDictionary)

輸出：

["USA": "Washington D.C.", "China": "Beijing", "India": "NEW DELHI"]