在oc中為了增強(qiáng)已有類的功能炼邀，我們經(jīng)常使用分類讶舰。使用分類捞蚂，我們可以在不破壞原有類的結(jié)構(gòu)的前提下妇押，對(duì)原有類進(jìn)行模塊化的擴(kuò)展。
但是在swift中沒(méi)有分類這種寫法了姓迅。相對(duì)應(yīng)的是swift中只有擴(kuò)展(Extensions)敲霍。
下面是swift中擴(kuò)展(Extensions)的說(shuō)明
擴(kuò)展就是向一個(gè)已有的類、結(jié)構(gòu)體丁存、枚舉類型或者協(xié)議類型添加新功能（functionality）肩杈。這包括在沒(méi)有權(quán)限獲取原始源代碼的情況下擴(kuò)展類型的能力（即逆向建模）。擴(kuò)展和 Objective-C 中的分類（categories）類似解寝。（不過(guò)與 Objective-C 不同的是扩然，Swift 的擴(kuò)展沒(méi)有名字。）
那么我們?cè)趺丛趕wift中實(shí)現(xiàn)oc中的分類呢聋伦？我們可以向蘋果學(xué)習(xí)夫偶。
同樣是UIView類，我們分別看看oc和swift不同的實(shí)現(xiàn)方式觉增。
1.我們先看看oc中的UIView
這是 UIView中的聲明的代碼
#ifndef SDK_HIDE_TIDE
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIView : UIResponder <NSCoding, UIAppearance, UIAppearanceContainer, UIDynamicItem, UITraitEnvironment, UICoordinateSpace, UIFocusEnvironment>
#else
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIView : UIResponder <NSCoding, UIAppearance, UIAppearanceContainer, UIDynamicItem, UITraitEnvironment, UICoordinateSpace>
#endif
+ (Class)layerClass; // default is [CALayer class]. Used when creating the underlying layer for the view.
- (instancetype)initWithFrame:(CGRect)frame NS_DESIGNATED_INITIALIZER;
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder NS_DESIGNATED_INITIALIZER;
@property(nonatomic,getter=isUserInteractionEnabled) BOOL userInteractionEnabled; // default is YES. if set to NO, user events (touch, keys) are ignored and removed from the event queue.
@property(nonatomic) NSInteger tag; // default is 0
@property(nonatomic,readonly,strong) CALayer *layer; // returns view's layer. Will always return a non-nil value. view is layer's delegate
#ifndef SDK_HIDE_TIDE
- (BOOL)canBecomeFocused NS_AVAILABLE_IOS(9_0); // NO by default
@property (readonly, nonatomic, getter=isFocused) BOOL focused NS_AVAILABLE_IOS(9_0);
#endif
+ (UIUserInterfaceLayoutDirection)userInterfaceLayoutDirectionForSemanticContentAttribute:(UISemanticContentAttribute)attribute NS_AVAILABLE_IOS(9_0);
@property (nonatomic) UISemanticContentAttribute semanticContentAttribute NS_AVAILABLE_IOS(9_0);
@end
其他的屬性和方法都是使用分類的方式進(jìn)行擴(kuò)展的兵拢。
下面是頁(yè)面渲染相關(guān)的屬性和方法
@interface UIView(UIViewRendering)
- (void)drawRect:(CGRect)rect;
- (void)setNeedsDisplay;
- (void)setNeedsDisplayInRect:(CGRect)rect;
@property(nonatomic) BOOL clipsToBounds; // When YES, content and subviews are clipped to the bounds of the view. Default is NO.
@property(nullable, nonatomic,copy) UIColor *backgroundColor UI_APPEARANCE_SELECTOR; // default is nil. Can be useful with the appearance proxy on custom UIView subclasses.
@property(nonatomic) CGFloat alpha; // animatable. default is 1.0
@property(nonatomic,getter=isOpaque) BOOL opaque; // default is YES. opaque views must fill their entire bounds or the results are undefined. the active CGContext in drawRect: will not have been cleared and may have non-zeroed pixels
@property(nonatomic) BOOL clearsContextBeforeDrawing; // default is YES. ignored for opaque views. for non-opaque views causes the active CGContext in drawRect: to be pre-filled with transparent pixels
@property(nonatomic,getter=isHidden) BOOL hidden; // default is NO. doesn't check superviews
@property(nonatomic) UIViewContentMode contentMode; // default is UIViewContentModeScaleToFill
@property(nonatomic) CGRect contentStretch NS_DEPRECATED_IOS(3_0,6_0) __TVOS_PROHIBITED; // animatable. default is unit rectangle {{0,0} {1,1}}. Now deprecated: please use -[UIImage resizableImageWithCapInsets:] to achieve the same effect.
@property(nullable, nonatomic,strong) UIView *maskView NS_AVAILABLE_IOS(8_0);
/*
-tintColor always returns a color. The color returned is the first non-default value in the receiver's superview chain (starting with itself).
If no non-default value is found, a system-defined color is returned.
If this view's -tintAdjustmentMode returns Dimmed, then the color that is returned for -tintColor will automatically be dimmed.
If your view subclass uses tintColor in its rendering, override -tintColorDidChange in order to refresh the rendering if the color changes.
*/
@property(null_resettable, nonatomic, strong) UIColor *tintColor NS_AVAILABLE_IOS(7_0);
/*
-tintAdjustmentMode always returns either UIViewTintAdjustmentModeNormal or UIViewTintAdjustmentModeDimmed. The value returned is the first non-default value in the receiver's superview chain (starting with itself).
If no non-default value is found, UIViewTintAdjustmentModeNormal is returned.
When tintAdjustmentMode has a value of UIViewTintAdjustmentModeDimmed for a view, the color it returns from tintColor will be modified to give a dimmed appearance.
When the tintAdjustmentMode of a view changes (either the view's value changing or by one of its superview's values changing), -tintColorDidChange will be called to allow the view to refresh its rendering.
*/
@property(nonatomic) UIViewTintAdjustmentMode tintAdjustmentMode NS_AVAILABLE_IOS(7_0);
/*
The -tintColorDidChange message is sent to appropriate subviews of a view when its tintColor is changed by client code or to subviews in the view hierarchy of a view whose tintColor is implicitly changed when its superview or tintAdjustmentMode changes.
*/
- (void)tintColorDidChange NS_AVAILABLE_IOS(7_0);
@end
2.這是swift中的代碼
UIView類中的聲明
@available(iOS 2.0, *)
public class UIView : UIResponder, NSCoding, UIAppearance, UIAppearanceContainer, UIDynamicItem, UITraitEnvironment, UICoordinateSpace, UIFocusEnvironment {
public class func layerClass() -> AnyClass // default is [CALayer class]. Used when creating the underlying layer for the view.
public init(frame: CGRect)
public init?(coder aDecoder: NSCoder)
public var userInteractionEnabled: Bool // default is YES. if set to NO, user events (touch, keys) are ignored and removed from the event queue.
public var tag: Int // default is 0
public var layer: CALayer { get } // returns view's layer. Will always return a non-nil value. view is layer's delegate
@available(iOS 9.0, *)
public func canBecomeFocused() -> Bool // NO by default
@available(iOS 9.0, *)
public var focused: Bool { get }
@available(iOS 9.0, *)
public class func userInterfaceLayoutDirectionForSemanticContentAttribute(attribute: UISemanticContentAttribute) -> UIUserInterfaceLayoutDirection
@available(iOS 9.0, *)
public var semanticContentAttribute: UISemanticContentAttribute
}
頁(yè)面渲染的代碼
extension UIView {
public func drawRect(rect: CGRect)
public func setNeedsDisplay()
public func setNeedsDisplayInRect(rect: CGRect)
public var clipsToBounds: Bool // When YES, content and subviews are clipped to the bounds of the view. Default is NO.
@NSCopying public var backgroundColor: UIColor? // default is nil. Can be useful with the appearance proxy on custom UIView subclasses.
public var alpha: CGFloat // animatable. default is 1.0
public var opaque: Bool // default is YES. opaque views must fill their entire bounds or the results are undefined. the active CGContext in drawRect: will not have been cleared and may have non-zeroed pixels
public var clearsContextBeforeDrawing: Bool // default is YES. ignored for opaque views. for non-opaque views causes the active CGContext in drawRect: to be pre-filled with transparent pixels
public var hidden: Bool // default is NO. doesn't check superviews
public var contentMode: UIViewContentMode // default is UIViewContentModeScaleToFill
// animatable. default is unit rectangle {{0,0} {1,1}}. Now deprecated: please use -[UIImage resizableImageWithCapInsets:] to achieve the same effect.
@available(iOS 8.0, *)
public var maskView: UIView?
/*
-tintColor always returns a color. The color returned is the first non-default value in the receiver's superview chain (starting with itself).
If no non-default value is found, a system-defined color is returned.
If this view's -tintAdjustmentMode returns Dimmed, then the color that is returned for -tintColor will automatically be dimmed.
If your view subclass uses tintColor in its rendering, override -tintColorDidChange in order to refresh the rendering if the color changes.
*/
@available(iOS 7.0, *)
public var tintColor: UIColor!
/*
-tintAdjustmentMode always returns either UIViewTintAdjustmentModeNormal or UIViewTintAdjustmentModeDimmed. The value returned is the first non-default value in the receiver's superview chain (starting with itself).
If no non-default value is found, UIViewTintAdjustmentModeNormal is returned.
When tintAdjustmentMode has a value of UIViewTintAdjustmentModeDimmed for a view, the color it returns from tintColor will be modified to give a dimmed appearance.
When the tintAdjustmentMode of a view changes (either the view's value changing or by one of its superview's values changing), -tintColorDidChange will be called to allow the view to refresh its rendering.
*/
@available(iOS 7.0, *)
public var tintAdjustmentMode: UIViewTintAdjustmentMode
/*
The -tintColorDidChange message is sent to appropriate subviews of a view when its tintColor is changed by client code or to subviews in the view hierarchy of a view whose tintColor is implicitly changed when its superview or tintAdjustmentMode changes.
*/
@available(iOS 7.0, *)
public func tintColorDidChange()
}
3.創(chuàng)建我們自己的extension
下面就讓我們嘗試一下，寫一個(gè)自己的swift分類
在get和set UIView的x和y屬性的時(shí)候代碼很繁瑣逾礁，如下：
//get x
var x = self.view.frame.origin.x
//set x
var rect = self.view.frame
rect.origin.x = 100
self.view.frame = rect
我們希望這里的代碼是這樣的
//get x
var x = self.view.x
//set x
self.view.x = 100
在oc中我們可以寫一個(gè)分類來(lái)實(shí)現(xiàn)说铃，這個(gè)難度不大。懶的自己寫的可以參照這個(gè)https://github.com/findM/UIView-Positioning
在swift中我們需要寫一個(gè)extension來(lái)實(shí)現(xiàn)
3.1 新建swift文件
新建swift文件.png
3.2 代碼實(shí)現(xiàn)
import Foundation
import UIKit
//private var PERSON_ID_NUMBER_PROPERTY = 0
extension UIView {
public var x: CGFloat{
get{
return self.frame.origin.x
}
set{
var r = self.frame
r.origin.x = newValue
self.frame = r
}
}
public var y: CGFloat{
get{
return self.frame.origin.y
}
set{
var r = self.frame
r.origin.y = newValue
self.frame = r
}
}
//其他的篇幅原因就不在這里一一實(shí)現(xiàn)了
}
全部的實(shí)現(xiàn)方法請(qǐng)參考這里https://github.com/findM/UIView-Positioning-Swift
