1. 精简代码 优点：代码在代码块中只在代码块中有效，减少对其他作用域命名污染。 缺点：可读性差。
NSURL *url = ({
[NSURL URLWithString:@"http://www.baidu.com"];
});
UILabel *testLabel = ({
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
label.text = @"test";
label.textAlignment = NSTextAlignmentCenter;
testLabel = label;
});
2. NSDictionary 另一种写法 (根据对象名字为key，值为value)
NSString *name = @"test";
NSNumber *userid = @(000111);
NSString *pwd = @"12345678";
NSDictionary *parm = NSDictionaryOfVariableBindings(name, userid, pwd);
{
name = test;
pwd = 12345678;
userid = 73;
}
3. 把tableview里cell的小对勾的颜色改成别的颜色
_mTableView.tintColor = [UIColor redColor];
4.navigationbar弄成透明的而不是带模糊的效果
[self.navigationBar setBackgroundImage:[UIImage new]
forBarMetrics:UIBarMetricsDefault];
self.navigationBar.shadowImage = [UIImage new];
self.navigationBar.translucent = YES;
5.改变uitextfield placeholder的颜色和位置
继承uitextfield，重写这个方法
- (void) drawPlaceholderInRect:(CGRect)rect {
[[UIColor blueColor] setFill];
[self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment];
}
6.在继承中，凡是要求子类重写父类的方法必须先调用父类的方法的，可以在父类方法名后面加上 NS_REQUIRES_SUPER. 子类重写这个
方法会自动警告提示要调用父类方法。
- (void)test NS_REQUIRES_SUPER;
7.判断VC是否已经加载过
if (self.isViewLoaded) {
<#statements#>
}
8. dictionary 追加 dictionary
[mutableDict addEntriesFromDictionary:appendDict]；
9. 获取当前屏幕显示的viewcontroller
- (UIViewController *)currentVC {
UIViewController *result = nil;
UIWindow * window = [[UIApplication sharedApplication] keyWindow];
if (window.windowLevel != UIWindowLevelNormal) {
NSArray *windows = [[UIApplication sharedApplication] windows];
for(UIWindow * tmpWin in windows) {
if (tmpWin.windowLevel == UIWindowLevelNormal) {
window = tmpWin;
break;
}
}
}
UIView *frontView = [[window subviews] objectAtIndex:0];
id nextResponder = [frontView nextResponder];
if ([nextResponder isKindOfClass:[UIViewController class]]) {
result = nextResponder;
}else {
result = window.rootViewController;
}
return result;
}
10. 捕获APP异常
NSSetUncaughtExceptionHandler (&UncaughtExceptionHandler);
void UncaughtExceptionHandler(NSException *exception) {
NSArray *arr = [exception callStackSymbols];//得到当前调用栈信息
NSString *reason = [exception reason];//非常重要，就是崩溃的原因
NSString *name = [exception name];//异常类型
#if DEBUG
NSString *msg = [NSString stringWithFormat:@"栈信息%@\n崩溃原因%@\n异常类型%@",arr[0], reason, name];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"崩溃日志" message:msg delegate:nil cancelButtonTitle:@"了解" otherButtonTitles:nil, nil];
[alert show];
#endif
DDLogCrash(@"崩溃日志: exception type : %@ \n crash reason : %@ \n call stack info : %@", name, reason, arr);
}
11. iOS 写文件
NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
NSString *h5LogFile = [documentPath stringByAppendingPathComponent:@"h5Log"];
NSFileManager *filemanager = [NSFileManager defaultManager];
// 判断文件大小
long long size = [[filemanager attributesOfItemAtPath:h5LogFile error:nil] fileSize] / (1024.0 * 1024);
if (size > 10) {
[filemanager removeItemAtPath:h5LogFile error:nil];
}
if (![filemanager fileExistsAtPath:h5LogFile])
{
[filemanager createFileAtPath:h5LogFile contents:nil attributes:nil];
}
NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:h5LogFile];
[fileHandle seekToEndOfFile];
NSDateFormatter *formatter;
if (formatter == nil) {
formatter = [[NSDateFormatter alloc] init];
}
formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
NSString *logStr = [NSString stringWithFormat:@"[%@ html5]:%@%@",[formatter stringFromDate:[NSDate date]],tag,txt];
logStr = [logStr stringByAppendingString:@"\r\n"];
NSData *data = [logStr dataUsingEncoding:NSUTF8StringEncoding];
NSData *aesData = [ZYAES256 AES256ParmEncryptWithKey:@"pamit" Encrypttext:data];
[fileHandle writeData:aesData];
[fileHandle closeFile];
logStr = nil;
12. NSDictionary 转换为model 系统方法 key需要和model属性对应
- (void)setValuesForKeysWithDictionary:(NSDictionary*)keyedValues;
[self.model setValuesForKeysWithDictionary:dict];
13.使用self.view.layer.borderWidth更好的方式圆角
CAShapeLayer *bordLayer = [CAShapeLayer layer];
bordLayer.frame = CGRectMake(0, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame));
bordLayer.lineWidth = 1.f;
bordLayer.strokeColor = [UIColor lightGrayColor].CGColor;
bordLayer.fillColor = [UIColor clearColor].CGColor;
UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame)) cornerRadius:3.0];
bordLayer.path = bezierPath.CGPath;
[self.view.layer insertSublayer:bordLayer atIndex:0];
14. @autoreleasepool 这段代码在每次遍历后释放所有autorelease对象
NSArray *urls = @[@"http://baidu.com",@"http://jd.com"];
for (NSURL *url in urls) {
@autoreleasepool {
NSError *error;
NSString *fileContents = [NSString stringWithContentsOfURL:url
encoding:NSUTF8StringEncoding error:&error];
// 处理
}
}