编程技巧 - 4

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26: 私有扩展 + 嵌套：

外露的两个方法接口：

#import <Foundation/Foundation.h>#import <AudioToolbox/AudioToolbox.h>@interface JSMessageSoundEffect : NSObject+ (void)playMessageReceivedSound;+ (void)playMessageSentSound;@end

用私有扩展“保护”的一个私有方法，并且你发现这样的嵌套会顺带保护它们的封装性：

#import "JSMessageSoundEffect.h"@interface JSMessageSoundEffect ()//私有扩展，就是不想这个方法暴露，并且下面两个赋参的方法也是私有,安全的+ (void)playSoundWithName:(NSString *)name type:(NSString *)type;@end@implementation JSMessageSoundEffect+ (void)playSoundWithName:(NSString *)name type:(NSString *)type{    NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:type];        if([[NSFileManager defaultManager] fileExistsAtPath:path]) {        SystemSoundID sound;        AudioServicesCreateSystemSoundID((__bridge CFURLRef)[NSURL fileURLWithPath:path], &sound);        AudioServicesPlaySystemSound(sound);    }    else {        NSLog(@"Error: audio file not found at path: %@", path);    }}+ (void)playMessageReceivedSound{    [JSMessageSoundEffect playSoundWithName:@"messageReceived" type:@"aiff"];}+ (void)playMessageSentSound{    [JSMessageSoundEffect playSoundWithName:@"messageSent" type:@"aiff"];}@end

27: 更简洁地取宽高

    CGSize size = self.view.frame.size;    CGRect tableFrame = CGRectMake(0.0f, 40.0f, size.width, size.height - 40 - INPUT_HEIGHT);

比你直接来两个 width 和 height 强得多啦。

28.取各种尺寸

/** @brief frame 左上角x view.frame.origin.x */#define VIEW_TLX(view) (view.frame.origin.x)/** @brief view frame 左上角y view.frame.origin.y */#define VIEW_TLY(view) (view.frame.origin.y)/** @brief view frame 右下角x */#define VIEW_BRX(view) (view.frame.origin.x + view.frame.size.width)/** @brief view frame 右下角y */#define VIEW_BRY(view) (view.frame.origin.y + view.frame.size.height)/** @brief view frame width */#define VIEW_W(view) (view.bounds.size.width)/** @brief view frame height */#define VIEW_H(view) (view.bounds.size.height)/** @brief CGRect 左上角x */#define FRAME_TLX(frame) (frame.origin.x)/** @brief CGRect 左上角y */#define FRAME_TLY(frame) (frame.origin.y)/** @brief CGRect width */#define FRAME_W(frame) (((frame).size).width)/** @brief CGRect height */#define FRAME_H(frame) (((frame).size).height)

分清楚Frame 和 Bounds的区别就可以明白左上右上的原理了。

29.优雅取消计时器

    if (_scrollTimer != nil) {        [_scrollTimer invalidate];        _scrollTimer = nil;    }

30.取消键盘一个巧做法：

@property (nonatomic, strong) id currentTextField;  //关闭键盘

代理方法设置同一对象：

#pragma mark - UITextFieldDelegate- (void)textFieldDidBeginEditing:(UITextField *)textField{      _currentTextField = textField;}

在适当位置关闭键盘：

[_currentTextField resignFirstResponder];//适当地方

31.尽量优雅地缩短你的代码！例如直接地判断返回布尔值！

self.inputToolBarView.sendButton.enabled = ([textView.text trimWhitespace].length > 0);

32.尽量贴近苹果公司的处理方法，无所不用其技

贴一个button的set方法，实现思想和底层的先release再retain非常非常相像：

#pragma mark - Setters- (void)setSendButton:(UIButton *)btn{    if(sendButton)        [sendButton removeFromSuperview];        sendButton = btn;    [self addSubview:self.sendButton];}

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