1、Xcode调试技巧—在系统抛出异常处设置断点有时候我们的程序不知道跑到哪个地方就 crash 了，而 crash 又很难重现。保守的做法是在系统抛出异常之前设置断点，具体来说是在 objc_exception_throw处设置断点。设置步骤为：首先在 XCode 按 CMD + 6，进入断点管理窗口；然后点击右下方的 +，增加新的 Symbolic Breakpoint，在 Symbol 一栏输入：objc_exception_throw，然后点击 done，完成。这样在 Debug 模式下，如果程序即将抛出异常，就能在抛出异常处中断了。比如在前面的代码中，我让 [firstObjctcrashTest]; 抛出异常。在 objc_exception_throw 处设置断点之后，程序就能在该代码处中断了，我们从而知道代码在什么地方出问题了。2、计算UIlabel 随字体多行后的高度+ (CGFloat)calcTextHeight:(int)textWidth text:(NSString *)text font:(int)fontSize { CGRect bounds, result; bounds = CGRectMake(0, 0, textWidth, 300); UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero]; label.font = [UIFont systemFontOfSize:fontSize]; label.text = text; result = [label textRectForBounds:bounds limitedToNumberOfLines:20]; return result.size.height;}或者CGSize requiredSize = [introduceLabel.text sizeWithFont:[UIFont systemFontOfSize:14] constrainedToSize:CGSizeMake(296.0f, FLT_MAX) lineBreakMode:UILineBreakModeTailTruncation];3、计算当前label随字体增加的长度（单行）CGSize boundingSize = CGSizeMake(320.0f, CGFLOAT_MAX);CGSize requiredSize = [status.user.username sizeWithFont:[UIFont boldSystemFontOfSize:13] constrainedToSize:boundingSize lineBreakMode:UILineBreakModeWordWrap];CGFloat requiredWidth = requiredSize.width;4、view控件加边框profileImageButton = [UIButton buttonWithType:UIButtonTypeCustom];[profileImageButton.layer setMasksToBounds:YES];[profileImageButton.layer setCornerRadius:4.0]; //设置矩形四个圆角半径[profileImageButton.layer setBorderWidth:1.0]; //边框宽度CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();CGColorRef colorref = CGColorCreate(colorSpace,(CGFloat[]){225.0/255.0, 225.0/255.0, 225.0/255.0, 1.0 });[profileImageButton.layer setBorderColor:colorref];//边框颜色 单独设置圆角[iconImage.layer setCornerRadius:4.0];[iconImage setClipsToBounds:YES];5、时区返回格式为数字(-12—+12) -(NSString *)getTimeZone{ NSString *zone = [[NSTimeZone systemTimeZone] description];//Europe/Berlin// America/New_York// Asia/Harbin //这三个可以用来测试exp:NSString *zone = [[NSTimeZone timeZoneWithName:@"America/New_York"] description]; NSString *time = [[zone componentsSeparatedByString:@"offset "] objectAtIndex:1]; int inv = [time intValue]; int result = inv / (60 * 60); if (result>0) { return [NSString stringWithFormat:@"+%d", result]; } return [NSString stringWithFormat:@"%d", result];}6、判定输入框不为空格以及空 NSString *_textField=[textField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; if ([_textField length] == 0) { UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"" message:@"评论内容不能为空！" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil]; [alertView show]; return NO; }7、根据当前键盘的高度来设置UITextField的位置- (void)textFieldDidBeginEditing:(UITextField *)textField{ [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardDidShowNotification object:nil];}- (void)keyboardWillShow:(id)sender { CGRect keyboardFrame; [[[((NSNotification *)sender) userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardFrame]; CGFloat keyboardHeight = CGRectGetHeight(keyboardFrame); [self.textImageView setFrame:CGRectMake(0, 416-keyboardHeight, 320, 45)];}8、设置label ,imageview,等点击时事件 UITapGestureRecognizer *imageTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapImage:)]; // [imageView setUserInteractionEnabled:YES]; 如果不能点击，设置可编辑 [imageView addGestureRecognizer:imageTap];9、判断剩余字数（字母数字符号两个算一个汉字）-(int)charNumber:(NSString *)strTemp{ int strLength =1; char *p =(char *) [strTemp cStringUsingEncoding:NSUnicodeStringEncoding]; for (int i=0; i<[strTemp lengthOfBytesUsingEncoding:NSUnicodeStringEncoding]; i++) { if (*p) { p++; strLength++; } else{ p++; } } return strLength/2;}10、UIWebView加载gif图片 ——这样可以解决gif图片不能下载到本地加载，使用SDWebImage down也出现界面不流畅，卡的问题UIWebView *webView = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, [homeTableCell getImageWidth:funnyPic], [homeTableCell getImageHeight:funnyPic])]; webView.backgroundColor = [UIColor clearColor]; // webView.scalesPageToFit = NO; 这一句我一直没搞清楚，有时对，有时不对的，注释了吧 //禁止webView的滑动 这样写主要是因为5.0以前的系统不能直接获取到webView.scrollView [(UIScrollView *)[[webView subviews] objectAtIndex:0] setBounces:NO];// 不让有白色的边，这个margin是必须的 NSString *html = [NSString stringWithFormat:@"",funnyPic.imageUrl]; [webView loadHTMLString:html baseURL:nil]; [imageView addSubview:webView];11、插入加载更多 tableview reloadData闪的问题 if (requestArray && [requestArray count] > 0) { int cellCount = [requestArray count];//获取一共有几行 NSMutableArray *indexArray = [[NSMutableArray alloc]initWithCapacity:10]; int numCountNow = [self.tableView numberOfRowsInSection:0]; for (; cellCount > 0; cellCount--) { NSIndexPath *path = [NSIndexPath indexPathForRow:numCountNow + cellCount - 1 inSection:0]; [indexArray addObject:path]; } [self.tableView insertRowsAtIndexPaths:indexArray withRowAnimation:UITableViewRowAnimationNone]; }12、Image 加载16进制的 图片（编译成freamwork的时候不能直接加载png图片，要转化）首先，使用UltraEdit把图片转化为16进制static const char _playerPause_icon [] = { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x11, 0x00, 0x00, 0x00, 0x1B, 0x08, 0x06, 0x00, 0x00, 0x00, 0x9A, 0xF6, 0x64, 0x9C, 0x00, 0x00, 0x00, 0x39, 0x49, 0x44, 0x41, 0x54, 0x38, 0x8D, 0x63, 0x64, 0x60, 0x60, 0x38, 0xC3, 0x80, 0x1D, 0x98, 0x60, 0x11, 0xC3, 0xAA, 0x96, 0xF1, 0xFF, 0xFF, 0xFF, 0xFF, 0xB1, 0x4A, 0x30, 0x32, 0x32, 0xA2, 0x8B, 0xE1, 0x52, 0xCB, 0x84, 0xC3, 0x15, 0x24, 0x81, 0x51, 0x43, 0x46, 0x0D, 0x19, 0x35, 0x64, 0xD4, 0x90, 0x51, 0x43, 0x46, 0x0D, 0xA1, 0xA7, 0x21, 0x00, 0xDD, 0x84, 0x09, 0xFD, 0x6B, 0x3C, 0x1F, 0xCB, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE, 0x42, 0x60, 0x82};然后加载 [playButton setImage:[UIImage imageWithData:[NSData dataWithBytes:_playerPause_icon length:sizeof(_playerPause_icon)/sizeof(char)]] forState:UIControlStateNormal];13、倒计时（剩余时间）- (void)timerFireMethod:(NSTimer*)theTimer{ id obj = [theTimer userInfo]; NSDateFormatter *f1 = [[NSDateFormatter alloc] init]; [f1 setDateFormat:@"yyyy-MM-dd HH:mm:ss.S"]; NSDate *theDay = [f1 dateFromString:(NSString*)obj]; [f1 release]; NSCalendar *cal = [NSCalendar currentCalendar];//定义一个NSCalendar对象 NSDate *today = [NSDate date];//得到当前时间 //用来得到具体的时差 unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit; NSDateComponents *d = [cal components:unitFlags fromDate:today toDate:theDay options:0]; NSString *countdown = [NSString stringWithFormat:@"%d日%d时%d分%d秒", [d month],[d day], [d hour], [d minute], [d second]]; self.timeLabel.text = countdown; return ; }14、九宫格或者其他类型的坐标设置 frame.size.width = 60;//设置按钮坐标及大小 frame.size.height = 60; frame.origin.x = (i%3)*(60 + 32)+40; frame.origin.y = floor(i/3)*(60 + 24)+60;15、appstore的几个跳转 1)跳转到应用：http://itunes.apple.com/cn/app/id566839843?mt=8 2)跳转到评论界面： NSString *m_appleID = @"566839843"; NSString *str = [NSString stringWithFormat:@"itms-apps://ax.itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?type=Purple+Software&id=%@",m_appleID]; [[UIApplication sharedApplication] openURL:[NSURL URLWithString:str]];16、显示多语言NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; NSArray *languages = [defaults objectForKey:@"AppleLanguages"]; NSString *localLangyage = [languages objectAtIndex:0]; if ([localLangyage isEqualToString:@"zh-Hans"]) {……}17、随机+ (NSString *)generateNonce { CFUUIDRef theUUID = CFUUIDCreate(NULL); CFStringRef string = CFUUIDCreateString(NULL, theUUID); NSString *returnString = [( NSString *)string copy]; CFRelease(string); CFRelease(theUUID); return returnString;}18、//刷新相应的cell- (void)getNewPersonCount:(NSNotification*)notifation{ int refreshIndex = [[notifation object]intValue]; NSIndexPath *indexPath = [NSIndexPath indexPathForRow:refreshIndex inSection:0]; [self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];}19、//存储到本地txt中- (void)editMenuOfBook{ NSString *filePath = @"/Users/Henghai/Desktop/BookReader/books/三国演义"; NSString *savefilePath = @"/Users/Henghai/Desktop/save.txt"; NSFileManager *fileManager =[NSFileManager defaultManager]; NSError *err = nil; NSArray *fileListOfFilePath = [fileManager contentsOfDirectoryAtPath:filePath error:&err]; int fileCount = [fileListOfFilePath count]; if (fileCount > 0) { NSString* str = [self joinString:fileListOfFilePath sep:@"\n"]; NSError *err = nil; [str writeToFile:savefilePath atomically:YES encoding:NSUTF8StringEncoding error:&err]; }}- (NSString*) joinString:(NSArray*)array sep:(NSString*)sep{ NSMutableString* str = [[NSMutableString alloc] initWithCapacity:[array count] * 2]; bool isFirst = YES; for (NSString* s in array) { if (isFirst) { isFirst = NO; } else { [str appendString:sep]; } [str appendString:[NSString stringWithFormat:@"%@",s]]; } return str;}20、Data that can be recreated but must persist for proper functioning of your app - or because customers expect it to be available for offline use - should be marked with the "do not back up" attribute. 想放到documents目录的话 设置do not back up属性就行了[[NSFileManager defaultManager] createDirectoryAtPath:temp withIntermediateDirectories:NO attributes:nil error:nil];NSURL *dbURLPath = [NSURL URLWithString:temp];[self addSkipBackupAttributeToItemAtURL:dbURLPath]; #include- (BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL
{
const char* filePath = [[URL path] fileSystemRepresentation];
const char* attrName = "com.apple.MobileBackup";
u_int8_t attrValue = 1;
int result = setxattr(filePath, attrName, &attrValue, sizeof(attrValue), 0, 0);
return result == 0;
}
21、字符串截取
（1）.截取字符串
NSString*string =@"sdfsfsfsAdfsdf";
string = [string substringToIndex:7];//截取下标7之后的字符串
NSLog(@"截取的值为：%@",string);
[string substringFromIndex:2];//截取下标2之前的字符串
NSLog(@"截取的值为：%@",string);
（2）.匹配字符串
NSString*string =@"sdfsfsfsAdfsdf";
NSRangerange = [stringrangeOfString:@"f"];//匹配得到的下标
NSLog(@"rang:%@",NSStringFromRange(range));
string = [string substringWithRange:range];//截取范围类的字符串
NSLog(@"截取的值为：%@",string);
（3）.分隔字符串
NSString*string =@"sdfsfsfsAdfsdf";
NSArray *array = [string componentsSeparatedByString:@"A"]; //从字符A中分隔成2个元素的数组
NSLog(@"array:%@",array); //结果是adfsfsfs和dfsdf
22.两次的间隔时间判断
//防止一直刷新积分 规定两次间隔20秒
NSTimeInterval _storedTimeInterval;
初始化：NSDate * nowDate = [NSDate date];
_storedTimeInterval = [nowDate timeIntervalSince1970];
判断：NSDate * nowDate = [NSDate date];
NSTimeInterval now = [nowDate timeIntervalSince1970];
int disValue = now - _storedTimeInterval;
if (disValue >= 20 ) {
_storedTimeInterval = now;
//XXXXXX处理
}
23、开启新线程
[NSThread detachNewThreadSelector:@selector(threadFunction) toTarget:self withObject:nil];
- (void)threadFunction{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingString:@"/test.txt"];
NSFileManager *fileManager =[NSFileManager defaultManager];
unsigned long long textSize = 0;
textSize = [[[fileManager attributesOfItemAtPath:path error:nil] objectForKey:NSFileSize] unsignedLongLongValue];
while (textSize == 0) {
[[NSRunLoop currentRunLoop] runMode:UITrackingRunLoopMode beforeDate:[NSDate distantFuture]];
textSize = [[[fileManager attributesOfItemAtPath:path error:nil] objectForKey:NSFileSize] unsignedLongLongValue];
}
}
首先是Run Loop的部分概念，它的作用就是循环、处理事件。具体来说有两个方面： 1. 定时启动任务（一般用和Timer协作）；2. 处理事件。
在单线程的app中，不需要注意Run Loop，但不代表没有。程序启动时，系统已经在主线程中加入了Run Loop。它保证了我们的主线程在运行起来后，就处于一种“等待”的状态（而不像一些命令行程序一样运行一次就结束了），这个时候如果有接收到的事件（Timer的定时到了或是其他线程的消息），就会执行任务，否则就处于休眠状态。
如果我们要写多线程的程序，可能就需要自己来管理Run Loop。
RunMode: NSDefaultRunLoopMode，可以把这个理解为一个”过滤器“，我们可以只对自己关心的事件进行监视。一般NSDefaultRunLoopMode是最常用的。
启动run loop的方法就是[[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantPast]]，它的说明如下：
Runs the loop once, blocking for input in the specified mode until a given date.
启动run loop一次，在特定的run loop mode下等待输入。
如果没有附加input source或是timer，或是过limitDate，run loop就会退出，并且方法返回NO。
下来是Run Loop的使用场合：
1. 使用port或是自定义的input source来和其他线程进行通信
2. 在线程（非主线程）中使用timer
3. 使用 performSelector...系列（如performSelectorOnThread, ...）
4. 使用线程执行周期性工作
run loop不需要创建，在线程中只需要调用[NSRunLoop currentRunLoop]就可以得到
假设我们想要等待某个异步方法的回调。比如connection。如果我们的线程中没有启动run loop，是不会有效果的（因为线程已经运行完毕，正常退出了）。我们可以用一个条件来运行run loop
BOOL done = NO;
do
{
［[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]］
}
while(!done);
这样就可以一直进行等待，直到在别的位置将done置为YES，表示任务完成。(转自http://www.cocoachina.com/bbs/read.php?tid=7851&keyword=NSRunLoop 7楼)
