- 通过使用范畴（category，范畴、分类），可以为任何已有的类添加方法。
- ⚠️ 建议使用带有前缀（bnr_）的方法:实现了使用范畴的方法时，如果在类中已经存在名称相同的另一个方法，这个使用了范畴的方法就会替换掉之前存在的方法。
- 应该使用范畴来给已存在的类增加新方法，而不要在范畴中替换已经存在的方法：这种情况下应该创建该类的子类。
示例一
为 NSDate 类添加一个创建日期的类方法：
-
NSDate+VowelCounting.h 文件
#import <Foundation/Foundation.h> @interface NSDate (VowelCounting) + (NSString *)bnr_createCustomDate; @end -
NSDate+VowelCounting.m 文件
#import "NSDate+VowelCounting.h" @implementation NSDate (VowelCounting) + (NSString *)bnr_createCustomDate { NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"yyyy-MM-dd"]; return [dateFormatter stringFromDate:[NSDate date]]; } @end -
使用
NSString *date = [NSDate bnr_createCustomDate];
示例二
为 UIView 增加一个分类，增加设置或者获取 UIView 视图位置的便捷语法。
这个分类应该经常可以在很多开源框架中看到。
UIView+Extension.h
#import <UIKit/UIKit.h>
@interface UIView (Extension)
// 推荐：CGFloat x = CGRectGetMinX(frame);
@property (nonatomic, assign) CGFloat x;
// 推荐：CGFloat y = CGRectGetMinY(frame);
@property (nonatomic, assign) CGFloat y;
@property (nonatomic, assign) CGFloat maxX;
@property (nonatomic, assign) CGFloat maxY;
@property (nonatomic, assign) CGFloat centerX;
@property (nonatomic, assign) CGFloat centerY;
// 推荐：CGFloat width = CGRectGetWidth(frame);
@property (nonatomic, assign) CGFloat width;
// 推荐：CGFloat height = CGRectGetHeight(frame);
@property (nonatomic, assign) CGFloat height;
@property (nonatomic, assign) CGSize size;
@property (nonatomic, assign) CGPoint origin;
@property (nonatomic, assign) CGFloat bottom;
@end
UIView+Extension.m
#import "UIView+Extension.h"
@implementation UIView (Extension)
#pragma mark - x
- (void)setX:(CGFloat)x {
CGRect frame = self.frame;
frame.origin.x = x;
self.frame = frame;
}
- (CGFloat)x {
return CGRectGetMinX(self.frame);
}
#pragma mark - y
- (void)setY:(CGFloat)y {
CGRect frame = self.frame;
frame.origin.y = y;
self.frame = frame;
}
- (CGFloat)y {
return CGRectGetMinY(self.frame);
}
#pragma mark - maxX
- (void)setMaxX:(CGFloat)maxX {
self.x = maxX - self.width;
}
- (CGFloat)maxX {
return CGRectGetMaxX(self.frame);
}
#pragma mark - maxY
- (void)setMaxY:(CGFloat)maxY {
self.y = maxY - self.height;
}
- (CGFloat)maxY {
return CGRectGetMaxY(self.frame);
}
#pragma mark - centerX
- (void)setCenterX:(CGFloat)centerX {
CGPoint center = self.center;
center.x = centerX;
self.center = center;
}
- (CGFloat)centerX {
return self.center.x;
}
#pragma mark - centerY
- (void)setCenterY:(CGFloat)centerY {
CGPoint center = self.center;
center.y = centerY;
self.center = center;
}
- (CGFloat)centerY {
return self.center.y;
}
#pragma mark - width
- (void)setWidth:(CGFloat)width {
CGRect frame = self.frame;
frame.size.width = width;
self.frame = frame;
}
- (CGFloat)width {
return CGRectGetWidth(self.frame);
}
#pragma mark - height
- (void)setHeight:(CGFloat)height {
CGRect frame = self.frame;
frame.size.height = height;
self.frame = frame;
}
- (CGFloat)height {
return CGRectGetHeight(self.frame);
}
#pragma mark - size
- (void)setSize:(CGSize)size {
CGRect frame = self.frame;
frame.size = size;
self.frame = frame;
}
- (CGSize)size {
return self.frame.size;
}
#pragma mark - orgin
- (void)setOrigin:(CGPoint)origin {
CGRect frame = self.frame;
frame.origin = origin;
self.frame = frame;
}
- (CGPoint)origin {
return self.frame.origin;
}
#pragma mark - bottom
- (void)setBottom:(CGFloat)bottom {
CGRect frame = self.frame;
frame.origin.y = bottom - frame.size.height;
self.frame = frame;
}
- (CGFloat)bottom {
CGRect frame = self.frame;
return CGRectGetMinY(frame) + CGRectGetHeight(frame);
}
@end
