Swift Collection Types

Collection types in Swift have arrays and dictionaries

The difference between an array and a dictionary is that the array is ordered, the dictionary type is unordered and the dictionary has a key value

1. Definition and updating of arrays

The definition of an array is array<sometype> or [SomeType]

var Yamanote line =["Nippori", "Eagle Valley"]

Yamanote Line. Count can be used to view the number of arrays

The Yamanote Line. IsEmpty can be used to determine if an array is empty

To add elements to an array, you can use the Append method

Yamanote Line. Append ("Ueno")

You can also use a combination assignment method

Yamanote Line +=["Akihabara"]

Yamanote Line +=["Kanda", "Tokyo"]//Add multiple elements at the same time

You can modify the value of an array by using the following method

Yamanote Line [0]= "Shinagawa"

Yamanote Line [1...2]=["Kobe", "Hiroshima"]//modification of the second third element

Inserting a value in an array can use the Insert method

Yamanote Line. Insert ("formerly", atindex:0)//Insert in item No. 0

Yamanote Line. Removeatindex (0)//the No. 0 item in an array returns the item that was removed

Remove Last item

Yamanote Line. Removelast ()//can move the last item in the divisor group

For (ordinal, station name) in enumerate (Yamanote line) {

println ("\ (serial number): \ (station name)")

}

The index in the array can be taken with this method

2. Creation and initialization of arrays

Initialization of an array can use literal

var a=[1,3,2]

You can also initialize an array using the constructor method of the array

Initializing an empty array can be written like this

var a=[int] ()

If each item in the array is the same

var threeint=[int] (count:3,repeatedvalue:0)

3. Definitions and updates of dictionaries

A dictionary can be defined using dictionary<keytype,valuetype> or [Keytype:valuetype]

Define an array using the Literal method

var airports:[string:string]=["Tyo": "Tokyo", "DUB": "Dublin"]

Use the Count property of the dictionary to see the number of elements in the dictionary

airports=[:] You can set the array to null

Use the IsEmpty property to see if the array is empty

You can add a value to the dictionary by using the subscript method

airports["SZX"]= "Shenzhen Bao ' an international airport"

You can also modify the values in the dictionary by subscript

airports["SZX"]= "Shenzhen Bao ' an international Airport 2 floor"

You can also use the method provided by the dictionary type to modify the elements in the dictionary, which returns an optional type

if (Airports.updatevalue ("Shenzhen Baoan International Airport", Forkey: "SZX")) {

println ("Update airport name succeeded!");

}else{

println ("Failed to update airport, no airport code")

}

There is no value for the optional type returned when the. Szx key is not present in the dictionary

Removing elements from a dictionary can use the Remove method

Airports.removevalueforkey ("SZX")//This method returns an optional type

Iterating through the elements in the dictionary can use the for

For (airport code, airport name) in airports{

println ("\ (airport code): \ (airport name)")

}

for (airport code) in airports.keys{

println (airport code)

}

for (airport name) in airports.values{

println (airport name)

}

Let airport code group =[string] (Airports.keys)

Let airport name Group =[string] (airports.values)

4. Creation and initialization of dictionaries

In addition to creating a dictionary in a literal way, you can create an array using the constructor provided by the dictionary type (note that the type of key is hash-capable)

var a=[int:string] ()

a[10]= "Arabic numerals ten"

a=[:]//Empty the dictionary

Swift Collection Types