Collection Types

• Dictionary

• Array

Array

An array stores multiple values with same type in an ordered list

Array Type Shorthand Syntax

Swift数组类型的完整表示为Array，SomeType是数组可以存储元素的类型名称

数组类型的简略表示为[SmoeType]

Array Literals

一个数组可以由array literal初始化。一个array literal为一个由square brackets包裹，由commas分割的数值的序列：

[value 1, value 2, value 3] 

Accessing and Modifying an Array

Property

• count

find number of items in an array

• isEmpty

check count property is equal to 0

Method

• append or +=

add a new item to the end of an array

• insert(newElementValue, atIndex:Int)

insert an item in an array

• removeAtIndex()

remove an item from an array and return the item

• removeLast()

remove last item from an array and return the item

subscript syntax

• change an existing value

1. var numberArray = [1,2,3,4,5,6]  

2. numberArray[0] = 0

3. //numberArray now [0,2,3,4,5,6,]

• change a range of values

1. var numberArray = [1,2,3,4,5,6]  

2. numberArray[0...3] = [0,0]  

3. //numberArray now [0,0,5,6]  

Iterating Over an Array

• iterate over entire values of array with for-in loop

1. for item in shoppingList {

2. println(item)

3. }

• iterate over entire values and index of array

1. for (index, value) in enumerate(shoppingList) {

2. println("Item \(index+1):\(value)")

3. }

Creating and Initializing an Array

• create an empty array

1. var someIns = [Int]()

2. println("someInts is of type [Int] with \(someInt.count) items.")

• create an array of certain size(called count ) and default value(called repeatedValue )

1. var threeDoubles = [Double](count: 3, repeatedValue: 0.0)  

2. println("13. threeDoubles: \(threeDoubles)")

3. var anotehrThrreeDoubles = [Double](count: 3, repeatedValue: 2.5)

4. var sixDoubles = threeDoubles + anotehrThrreeDoubles5. println("13. sixDoubles: \(sixDoubles)")

Dictionary

Each value in dictionary is associated with a unique key. Items in dictionary don't have an order

Dictionary Type Shorthand syntax

Swift Dictionary类型的完整表示为Dictionary，key is type of key, value is type of value

数组类型的简略表示为[key, value]

Dictionary Literal

1. var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]

Accessing and Modifying a Dictionary

Property

• count

• isEmpty

Methods

• updateValue(forKey:)

The type of return result is optional(String? ), and the return result is old value.

If there is no value for the key, the dictionary will add this element and return nil

1. if let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB") {

2.    println("4. The old value for DUB was \(oldValue).")

3. }

Subscript Syntax

• add an element with new key

1. airports​[​"LHR"​] = ​"London"

• modify an element with a key

1. airports["LHR"] = "London Heathrow"

• remove an element with a key

1. airports["APL"] = "Apple International"

2. println("5. \(airports)")

3. airports["APL"] = nil

4. println("5. \(airports)")

Iterating Over a Dictionary

• iterate key and value

1. for (airportCode, airportName)  in airports {

2.    println("6. \(airportCode): \(airportName)")

3. }

• iterate key

1. for airportCode in airports.keys{

2.    println("7. Airport code: \(airportCode)")

3. }

• iterate value

1. for airportName in airports.values {

2.    println("8. Airport name: \(airportName)")

3. }

• use a dictionary's key to initialize an array

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

2. println(airportCodes)

• use a dictionary's value to initialize an array

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

2. println(airportNames)

Creating an Empty Dictionary

1. var namesOfIntegers = [Int: String]()

Hash Values for Dictionary Key Types

The type of key must provide a way to compute a hash value for itself

Hashable type:

• Int

• String

• Double

• Bool

• Enumeration (member values without associated values)