iOS 笔记

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

}

}

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