2014年8月1日 星期五

Swift Language Guide - Collection

Swift Language Guide - Collection

Array

Initialize

var a: [String] = ["a", "b", "c"]
var b: [String] = []
var c = ["a", "b", "c"]
var d = []                  <-- OK, NOT suggest

c += "abc"
d += "abc"  <-- Error

var e = [Int]()     <-- an empty of Integer Array

var f = [Double](count: 3, repeatedValue: 10)   <-- [10.0, 10.0, 10.0]

Operations

func dumpArr<T>(arr: [T]) {
    for (i, elm) in enumerate(arr) {
        println("\(i) = \(elm)")
    }
    println()
}

var arr = ["a", "b", "c"]

arr += "abc"                    <-- ["a", "b", "c", "abc"]

for str in arr {
    println(str)
}

arr += ["def", "ghi"]           <-- ["a", "b", "c", "abc", "def", "ghi"]
dumpArr(arr)

println(arr[0])

arr[0] = "zzz"                  <-- ["zzz", "b", "c", "abc", "def", "ghi"]
dumpArr(arr)

arr[2...4] = ["yyy", "xxx"]     <-- ["zzz", "b", "yyy", "xxx", "ghi"] the 4-index element is removed
dumpArr(arr)

arr[2..<4] = ["mmm", "nnn"]     <-- ["zzz", "b", "mmm", "nnn", "ghi"]
dumpArr(arr)

arr.insert("ggg", atIndex: 3)   <-- ["zzz", "b", "mmm", "ggg", "nnn", "ghi"]
dumpArr(arr)

arr.removeAtIndex(0)            <-- ["b", "mmm", "ggg", "nnn", "ghi"]
dumpArr(arr)

arr.removeLast()                <-- ["b", "mmm", "ggg", "nnn"]
dumpArr(arr)

arr = []                        <-- empty array
println(arr.count)              <-- 0

arr[2...4] = ["yyy", "xxx"] <-- ["zzz", "b", "yyy", "xxx", "ghi"] the 4-index element is removed_

Dictionary

Initialize

var b:[String: Int] = ["a": 1, "b": 2]
var c = [String: String]()
var a = ["a": 1, 2: "b"]    <-- OK, NOT Suggest

Operations

func dumpDict<T, U>(dict: [T:U]) {
    for (key, value) in dict {
        println("(\(key), \(value))")
    }
    println()
}

var dict = [String: Int]()

dict["a"] = 1
dict["b"] = 2

dumpDict(dict)

let old1 = dict.updateValue(3, forKey: "a")
println("old value is \(old1)")

let old2: Int! = dict.updateValue(4, forKey: "c")
println("old value is \(old2)")

if let old3 = dict.updateValue(5, forKey: "d") {
    println("old value is \(old3)")
}
else {
    println("No element in dict")
}

dict["a"] = nil     <-- remove element for key "a"
dumpDict(dict)

if let old4 = dict.removeValueForKey("a") {
    println("old value of \"a\" is \(old4)")
}
else {
    println("No element in dict")
}

for key in dict.keys {
    println("(\(key), \(dict[key]))")
}

for key in dict.keys {
    println("(\(key), \(dict[key]))")
}

var keys = Array(dict.keys)             <-- Array
for (i, elm) in enumerate(keys) {
    println("\(i) = \(elm)")
}

var values = Array(dict.values)         <-- Array
for (i, elm) in enumerate(values) {
    println("\(i) = \(elm)")
}

dict = [:]                              <-- empty dictionary
println(dict.count)                     
  • dict.updateValue return OPTIONAL VALUE
  • dict.removeValueForKey return OPTIONAL VALUE
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