2019独角兽企业重金招聘Python工程师标准>>> 
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iOS simulator运行程序出现问题：An error was encountered while running (Domain = FBSOpenApplicationErrorDomain, Code = 4)
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解决办法：iOS Simulator----> Reset Contents and Settings ----> Reset（其实就是还原模拟器－_－!!!）
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xcode6中添加pch文件：
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1.Command + N 然后在Other里面选择PCH File --- >Next --->Save As（这里写工程名字格式为xxx.pch）--->Create
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2.在Build Settings里面找到Prefix Header,双击添加pch文件路径，格式为是 xxx/xxx.pch
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ios8tableView分割线左边空白问题 －－－viewdidload里面调用[self viewDidLayoutSubviews];方法
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-(void)viewDidLayoutSubviews { if ([myTableView respondsToSelector:@selector(setSeparatorInset:)]) { [myTableView setSeparatorInset:UIEdgeInsetsMake(0,0,0,0)]; } if ([myTableView respondsToSelector:@selector(setLayoutMargins:)]) { [myTableView setLayoutMargins:UIEdgeInsetsMake(0,0,0,0)]; } } -(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath { if ([cell respondsToSelector:@selector(setSeparatorInset:)]) { [cell setSeparatorInset:UIEdgeInsetsZero]; } if ([cell respondsToSelector:@selector(setLayoutMargins:)]) { [cell setLayoutMargins:UIEdgeInsetsZero]; } } -
报错：Link against the umbrella framework 'System.framework' instead. for architecture x86_64
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在用x6写gcd的时候，由于没有代码提示，误以为x6里面没有了libdispatch.dylib框架，所以导入了，然后报上面的错误，又继续导入了libSystem.dylib框架，仍然报如上错误。于是把刚才导入的两个框架删掉了，然后没问题了，总结就是x6代码提示的问题。
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报错：Dwarf Exception Unwind Info (__eh_frame) in AppDelegate.o
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加上libc++.dylib，问题解决
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报错：Unknown type name “CGFloat” 或者 Unknown type name 'UIColor'
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我的是extern const引起的，在使用到extern const的类里面添加头文件#import
就行了 -
Xcode6编译SDWebImage报错：Use of undeclared identifier '_executing'；Use of undeclared identifier '_finished'；
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解决办法：在SDWebImageDownloaderOperation.m下面的
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@implementation SDWebImageDownloaderOperation{}下面添加如下代码:
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@synthesize executing = _executing ;
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@synthesize finished = _finished;
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xcode6.0以后地图无法定位的问题
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//在ios 8.0上要授权 if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) { [myLocationManager requestWhenInUseAuthorization]; //调用了这句,在程序前台运行的时候，就会弹出允许框了允许定位 // [myLocationManager requestAlwaysAuthorization];//程序前台后台运行一直允许定位 } -
记住要在info.plist里面添加缺省字段NSLocationWhenInUseUsageDescription或者NSLocationAlwaysUsageDescription(具体添加哪个根据你上面设置而定)
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iOS8系统下的无法弹出通知：Attempting to schedule a local notification ，with an alert but haven't received permission from the user to display alerts，with a sound but haven't received permission from the user to play sounds
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原因在于iOS8系统变更了注册方法，需要在ApplicationDelegate里面注册通知才可以。
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再appdelegate.m的didFinishLaunchingWithOptions方法里面，添加如下代码:
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if ([UIApplication instancesRespondToSelector:@selector(registerUserNotificationSettings:)]) { [application registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeAlert|UIUserNotificationTypeBadge|UIUserNotificationTypeSound categories:nil]]; } -
ios8系统下的推送：registerForRemoteNotificationTypes: is not supported in iOS 8.0 and later
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// IOS8系统以后需要这么写 if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) { [[UIApplication sharedApplication] registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeSound | UIUserNotificationTypeAlert | UIUserNotificationTypeBadge) categories:nil]]; [[UIApplication sharedApplication] registerForRemoteNotifications]; } else { //这里还是原来的代码 [[UIApplication sharedApplication] registerForRemoteNotificationTypes: (UIUserNotificationTypeBadge | UIUserNotificationTypeSound | UIUserNotificationTypeAlert)]; }
运行报错：No architectures to compile for (ONLY_ACTIVE_ARCH=YES, active arch=x86_64, VALID_ARCHS=i386).
解决办法：这是缺少arm64的原因导致，需要在下图两个地方的valid architectures里面添加上arm64
报错：could not build module 'Foundation'
解决方法：在Build Settings 下的 Apple LLVM xxx - Language (xxx代表的是你当前的xcode默认的LLVM编译器版本)，找到Compile Sources As ,将其改成 Objective-C即可。默认的是第一个“According to File Type”，如此修改的意思是把工程按照哪一种语言进行编译，可根据实际情况选择编译语言。
报错：library not found for -
出现此种错误的原因是因为，我们工程里面使用的第三方库。当xcode进行编译的时候，没有找到此库文件。所以，我们需要在Build Settings下面的Search Paths里面的Library Search Paths中添加该库所在的文件夹的路径。这样编译的时候就可以找到该库了。
报错：[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object'
将NSMutableDictionary *uuDic = [ [NSUserDefaults standardUserDefaults] objectForKey:@"mycollect"];改成NSMutableDictionary *uuDic = [NSMutableDictionary dictionaryWithDictionary:[ [NSUserDefaults standardUserDefaults] objectForKey:@"mycollect"]];
报错：[UIImage imageWithRenderingMode:]: unrecognized selector sent to instance 0x2017c720
[UIImage imageWithRenderingMode:]这个方法在ios7以上的版本里面才支持，所以需要判断一下当前的系统版本
报错：Multiple build commands for output file /xxx
选中工程，点击 Build Phases， 展开Copy Bundle Resources，删除里面的刚才提示警告的文件,一般为红色的名字的文件。 或者有多个相同的文件，删除一个多余的。
警告：Block implicitly retains 'self'; explicitly mention 'self' to indicate this
选中工程，点击 Building Settings ，搜索 implicit retain of 'self' ，将对应的值改为NO
报错：Safe Area Layout Guide before iOS 9.0
