jiangleligejiang / JNote

记录相关日常笔记

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Swift相关语言特性 #7

Open jiangleligejiang opened 5 years ago

jiangleligejiang commented 5 years ago

使用struct更好构建常量的调用


public struct Specs {
public struct Color {
    public let tint = UIColor(hex: 0x3b5998)
    public let red = UIColor.red
    public let white = UIColor.white
    public let black = UIColor.black
    public let gray = UIColor.lightGray
}

public static var color: Color {
    return Color()
}

}

调用方式：
```swift
view.backgroundColor = Specs.color.gray

jiangleligejiang commented 5 years ago

`typealias`的使用

使用typealias使代码更规范


//定义一个<k,v>为<String,String>的Dictionary
typealias RowModel = [String : String]

//使用更具意义的名词来代替类型名词 typealias Location = CGPoint typealias Distance = Double func distanceBetweenPoint(location: Location, toLocation: Location) -> Distance { let dx = Distance(location.x - toLocation.x) let dy = Distance(location.y - toLocation.y) return sqrt(dx dx + dy dy) } let origin: Location = Location(x: 0, y: 0) let point: Location = Location(x: 1, y: 1) let distance: Distance = distanceBetweenPoint(origin, toLocation: point)

- 使用`typealias`时，必须要保证泛型中需要确定类型
```swift
class Person<T> {}
typealias WorkId = Person<String>
typealias Worker = Person<WorkId>

jiangleligejiang commented 5 years ago

函数参数不变性

通常情况下，函数传入的参数都为不可变的，若需要参数是引用传递，则要使用inout关键字
func quick_sort_arr( A: inout Array<Int>, start:Int, end:Int) {
if start < end {
let partition = quick_sort_partition(A: &A, start: start, end: end)
quick_sort_arr(A: &A, start: start, end: partition-1)
quick_sort_arr(A: &A, start: partition+1, end: end)
}
}

jiangleligejiang commented 5 years ago

associatedtype的使用

由于swift中protocol不能使用<T>这种形式来定义泛型，因此，提供了associatedtype来定义泛型。
public protocol ObservableConvertibleType {
/// Type of elements in sequence.
associatedtype Element

@available(*, deprecated, message: "Use `Element` instead.")
typealias E = Element

/// Converts `self` to `Observable` sequence.
///
/// - returns: Observable sequence that represents `self`.
func asObservable() -> Observable<Element>

}

jiangleligejiang commented 5 years ago