Swift Introduction | Arrays and Dictionaries | Working with Dictionaries

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• Swift

Like arrays, dictionaries are objects with properties and methods. Call these methods to manipulate dictionary contents. Unlike arrays, dictionaries do not need an insertion method because you can add a new value simply by specifying a key.

Removing the Value for a Specified Key

dictionary.removeValueForKey(key)

Removing All Values

dictionary.removeAll()

Retrieving All Keys

variable = dictionary.keys

Retrieving All Stored Values

variable = dictionary.values

Retrieving the Number of Elements

variable : Int = dictionary.count

Pay particular attention to keys and values. These properties store the keys and values respectively. Their return values are instances of an unfamiliar collection class called LazyBidirectionalCollection, but you can retrieve their values sequentially with for-in.

The following example works with a dictionary.

var data:[String:Int] = ["Korean":98,"Mathematics":76,"English":54]
let keys = data.keys
let vals = data.values
for key in keys {
    println(key)
}
for val in vals {
    println(val)
}

This code retrieves the dictionary’s keys and values, then prints them with for-in. The stored keys and values are displayed.