前言
记录一些代码小技巧持续更新!
Xcode12模板位置:
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/Library/Xcode/Templates/File Templates/iOS/Source/Cocoa Touch Class.xctemplate
Objective-C tips
1、使控件从导航栏以下开始
self.edgesForExtendedLayout=UIRectEdgeNone;
2、将navigation返回按钮文字position设置不在屏幕上显示
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(NSIntegerMin, NSIntegerMin) forBarMetrics:UIBarMetricsDefault];
3、解决ScrollView等在viewController无法滚动到最顶部
//自动滚动调整，默认为YES
self.automaticallyAdjustsScrollViewInsets = NO;
4、隐藏navigationBar上返回按钮
[self.navigationController.navigationItem setHidesBackButton:YES];
[self.navigationItem setHidesBackButton:YES];
[self.navigationController.navigationBar.backItem setHidesBackButton:YES];
5、当tableView占不满一屏时，去除上下边多余的单元格
self.tableView.tableHeaderView = [UIView new];
self.tableView.tableFooterView = [UIView new];
6、显示完整的CellSeparator线
-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath{
if ([cell respondsToSelector:@selector(setSeparatorInset:)]) {
[cell setSeparatorInset:UIEdgeInsetsZero];
}
if ([cell respondsToSelector:@selector(setPreservesSuperviewLayoutMargins:)]) {
[cell setPreservesSuperviewLayoutMargins:NO];
}
if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {
[cell setLayoutMargins:UIEdgeInsetsZero];
}
}
7、滑动的时候隐藏navigation bar
navigationController.hidesBarsOnSwipe = Yes;
8、将Navigationbar变成透明而不模糊
[self.navigationController.navigationBar setBackgroundImage:[UIImage new]
forBarMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar .shadowImage = [UIImage new];
self.navigationController.navigationBar .translucent = YES;
9、NSString常用处理方法
//截取字符串
NSString *interceptStr1 = @"Tate_zwt";
interceptStr1 = [interceptStr1 substringToIndex:3];//截取下标3之前的字符串
NSLog(@"截取的值为:%@",interceptStr1);//截取的值为:Tat
NSString *interceptStr2 = @"Tate_zwt";
NSRange rang = {3,1};
interceptStr2 = [interceptStr2 substringWithRange:rang];//截取rang范围的字符串
NSLog(@"截取的值为:%@",interceptStr2);//截取的值为:e
NSString *interceptStr3 = @"Tate_zwt";
interceptStr3 = [interceptStr3 substringFromIndex:3];//截取下标3之后的字符串
NSLog(@"截取的值为:%@",interceptStr3);//截取的值为:e_zwt
//匹配字符串
NSString *matchingStr = @"Tate_zwt";
NSRange range = [matchingStr rangeOfString:@"t"];//匹配得到的下标
NSLog(@"rang:%@",NSStringFromRange(range));//rang:{2, 1}
matchingStr = [matchingStr substringWithRange:range];//截取范围类的字符串
NSLog(@"截取的值为:%@",matchingStr);//截取的值为:t
//分割字符串
NSString *splitStr = @"Tate_zwt_zwt";
NSArray *array = [splitStr componentsSeparatedByString:@"_"]; //从字符A中分隔成2个元素的数组
NSLog(@"array:%@",array); //输出3个对象分别是:Tate,zwt,zwt
//拼接字符串
NSMutableString *appendStr = [NSMutableString string];
//使用逗号拼接
//[append appendFormat:@"%@zwt", append.length ? @"," : @""];
[appendStr appendString:@"我是"];
[appendStr appendString:@"Tate-zwt"];
NSLog(@"%@",appendStr);//输出:我是Tate-zwt
//替换字符串
NSString *replaceStr = @"我是 Tate-zwt";
replaceStr = [replaceStr stringByReplacingOccurrencesOfString:@" " withString:@""];
NSLog(@"%@",replaceStr);//输出:我是Tate-zwt
//判断字符串内是否还包含特定的字符串(前缀，后缀)
NSString *hasStr = @"Tate.zwt";
[hasStr hasPrefix:@"Tate"] == 1 ? NSLog(@"YES") : NSLog(@"NO"); //前缀
[hasStr hasSuffix:@".zwt"] == 1 ? NSLog(@"YES") : NSLog(@"NO"); // 后缀
//字符串是否包含特定的字符
NSString *containStr = @"iOS Developer,喜欢做有趣的产品";
NSRange rangeDeveloper = [containStr rangeOfString:@"Developer"];
NSRange rangeProduct = [containStr rangeOfString:@"Product"];
rangeDeveloper.location != NSNotFound == 1 ? NSLog(@"YES") : NSLog(@"NO");
rangeProduct.location != NSNotFound == 1 ? NSLog(@"YES") : NSLog(@"NO");
10、UIPageControl如何改变点的大小?
重写setCurrentPage方法即可:
- (void)setCurrentPage:(NSInteger)page {
[super setCurrentPage:page];
for (NSUInteger subviewIndex = 0; subviewIndex < [self.subviews count]; subviewIndex++) {
UIView *subview = [self.subviews objectAtIndex:subviewIndex];
UIImageView *imageView = nil;
if (subviewIndex == page) {
CGFloat w = 8;
CGFloat h = 8;
imageView = [[UIImageView alloc] initWithFrame:CGRectMake(-1.5, -1.5, w, h)];
imageView.image = [UIImage imageNamed:@"banner_red"];
[subview setFrame:CGRectMake(subview.frame.origin.x, subview.frame.origin.y, w, h)];
} else {
CGFloat w = 5;
CGFloat h = 5;
imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, w, h)];
imageView.image = [UIImage imageNamed:@"banner_gray"];
[subview setFrame:CGRectMake(subview.frame.origin.x, subview.frame.origin.y, w, h)];
}
imageView.tag = 10010;
UIImageView *lastImageView = (UIImageView *) [subview viewWithTag:10010];
[lastImageView removeFromSuperview]; //把上一次添加的view移除
[subview addSubview:imageView];
}
}
11、如何改变多行UILabel的行高？
Show me the code：
_promptLabel = [UILabel new];
NSString *labelText = @"Talk is cheap\nShow me the code";
_promptLabel.text = labelText;
_promptLabel.numberOfLines = 2;
_promptLabel.font = [UIFont systemFontOfSize:14];
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:labelText];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:10]; //调整行间距
[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [labelText length])];
_promptLabel.attributedText = attributedString;
[_promptLabel sizeToFit];
[self.view addSubview:_promptLabel];
12、如何让Label等控件支持HTML格式的代码？
使用NSAttributedString:
NSString *htmlString = @"Tate《iOS Develop Tips》get Tate_zwt 打赏 100 金币";
NSAttributedString *attributedString = [[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType } documentAttributes:nil error:nil];
_contentLabel.attributedText = attributedString;
13、如何让Label等控件同时支持HTML代码和行间距？
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithData:[_open_bonus_article dataUsingEncoding:NSUnicodeStringEncoding] options:@{ NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType } documentAttributes:nil error:nil];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:12]; //调整行间距
[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [attributedString length])];
_detailLabel.attributedText = attributedString;
[_detailLabel sizeToFit];
14、pop回根控制器视图
//这里也可以指定pop到哪个索引控制器
[self.navigationController popToViewController: [self.navigationController.viewControllers objectAtIndex: ([self.navigationController.viewControllers count] - 3)] animated:YES];
//或者
[self.navigationController popToRootViewControllerAnimated:YES];
15、dismiss回根控制器视图(PS：只能返回两层)
if ([self respondsToSelector:@selector(presentingViewController)]){
self.presentingViewController.view.alpha = 0;
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:YES completion:nil];
}else {
self.parentViewController.view.alpha = 0;
[self.parentViewController.parentViewController dismissViewControllerAnimated:YES completion:nil];
}
//或者
if ([self respondsToSelector:@selector(presentingViewController)]){
[self.presentingViewController.presentingViewController dismissViewControllerAnimated:YES completion:nil];
}else {
[self.parentViewController.parentViewController dismissViewControllerAnimated:YES completion:nil];
}
16、两个控制器怎么无限push?
NSMutableArray *vcArr = [self.navigationController.viewControllers mutableCopy];
[vcArr removeLastObject];
[vcArr addObject:loginVC];
[self.navigationController setViewControllers:vcArr animated:YES];
17、NSDictionary 怎么转成NSString
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:response.data options:0 error:0];
NSString *dataStr = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
18、获取系统可用存储空间 ，单位：字节
/**
* 获取系统可用存储空间
*
* @return 系统空用存储空间，单位：字节
*/
-(NSUInteger)systemFreeSpace{
NSString *docPath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSDictionary *dict=[[NSFileManager defaultManager] attributesOfFileSystemForPath:docPath error:nil];
return [[dict objectForKey:NSFileSystemFreeSize] integerValue];
}
19、有时OC调用JS代码没反应？
stringByEvaluatingJavaScriptFromString 必须在主线程里执行
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf.webView stringByEvaluatingJavaScriptFromString:jsStr];
// [weakSelf.webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"alertTest('%@');", @"test"]];
});
20、获取相册图片的名称及后缀
#pragma mark UIImagePickerControllerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{
//获取图片的名字
__block NSString* fileName;
NSURL *imageURL = [info valueForKey:UIImagePickerControllerReferenceURL];
ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
{
ALAssetRepresentation *representation = [myasset defaultRepresentation];
fileName = [representation filename];
NSLog(@"fileName : %@",fileName);
self.imageFileName = fileName;
};
ALAssetsLibrary* assetslibrary = [[ALAssetsLibrary alloc] init];
[assetslibrary assetForURL:imageURL
resultBlock:resultblock
failureBlock:nil];
}
21、UITableView 自动滑动到某一行
//四种枚举样式
UITableViewScrollPositionNone,
UITableViewScrollPositionTop,
UITableViewScrollPositionMiddle,
UITableViewScrollPositionBottom
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
//第一种方法
[tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
//第二种方法
[self.tableVieW selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionTop];
22、 Xcode8注释快捷键不能使用的解决方法：
In Terminal: sudo /usr/libexec/xpccachectl
最近使用CocoaPods来添加第三方类库，无论是执行pod install还是pod update都卡在了Analyzing dependencies不动
原因在于当执行以上两个命令的时候会升级CocoaPods的spec仓库，加一个参数可以省略这一步，然后速度就会提升不少。加参数的命令如下：
pod install --verbose --no-repo-update
pod update --verbose --no-repo-update
你可以 cd ~/.cocoapods/repos/ 到这个目录下 执行du -sh * 看下下载了多少
23、获取模拟器沙盒路径
NSArray *aryPath=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
//沙盒路劲
NSString *strDocPath=[aryPath objectAtIndex:0];
24、tableView.tableHeaderView 一些设置方法
_tableView.tableHeaderView = _heatOrTimeView;
[_heatOrTimeView mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.right.top.equalTo(_tableView);
make.width.equalTo(_tableView);
make.height.mas_equalTo(@36);
}];
// 如果是动态改变高度的话这里要加上以下代码
// [_tableView layoutIfNeeded];
// [_tableView beginUpdates]; 这个是增加动画效果
// [_tableView endUpdates];
// _tableView.tableHeaderView = _heatOrTimeView;
25、约束如何做UIView动画？
1、把需要改的约束Constraint拖条线出来，成为属性
2、在需要动画的地方加入代码，改变此属性的constant属性
3、开始做UIView动画，动画里边调用layoutIfNeeded方法
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *buttonTopConstraint;
self.buttonTopConstraint.constant = 100;
[UIView animateWithDuration:.5 animations:^{
[self.view layoutIfNeeded];
}];
26、删除某个view所有的子视图
[[someView subviews] makeObjectsPerformSelector:@selector(removeFromSuperview)];
27、将一个view放置在其兄弟视图的最上面
[parentView bringSubviewToFront:yourView]
28、将一个view放置在其兄弟视图的最下面
[parentView sendSubviewToBack:yourView]
29、layoutSubviews方法什么时候调用？
1、init方法不会调用
2、addSubview方法等时候会调用
3、bounds改变的时候调用
4、scrollView滚动的时候会调用scrollView的layoutSubviews方法(所以不建议在scrollView的layoutSubviews方法中做复杂逻辑)
5、旋转设备的时候调用
6、子视图被移除的时候调用参考请看：[http://blog.logichigh.com/2011/03/16/when-does-layoutsubviews-get-called/](http://blog.logichigh.com/2011/03/16/when-does-layoutsubviews-get-called/)
30、isKindOfClass和isMemberOfClass的区别
isKindOfClass可以判断某个对象是否属于某个类，或者这个类的子类。
isMemberOfClass更加精准，它只能判断这个对象类型是否为这个类(不能判断子类)
31、IOS App开启iTunes文件共享（文稿）
通过在app工程的Info.plist文件中指定Application supports iTunes file sharing关键字，并将其值设置为YES。
我们可以很方便的打开app与iTunes之间的文件共享。
但这种共享有一个前提：App必须将任何所需要共享给用户的文件，都要存放在/Documents目录下，即在app安装时自动创建的app的主目录。
32、去掉UITabBar的分割线的方法
[[UITabBar appearance] setShadowImage:[UIImage new]];
[[UITabBar appearance] setBackgroundImage:[UIImage new]];
33、URLWithString:(NSString *)str relativeToURL:(NSURL *)baseURL中baseURL拼接字段的问题
问题描述
URLWithString:(NSString *)str relativeToURL:(NSURL *)baseURL中baseURL结尾字段的相关问题拼接后被去掉的问题，情况如下：
NSURL *baseUrl = [NSURL URLWithString:@"http://test.com/v1"];
NSLog(@"%@", baseUrl);
NSURL *newURL = [NSURL URLWithString:@"/test/get_all" relativeToURL: baseUrl];
NSLog(@"newURL:%@",[newURL absoluteString]);//http://test.com/test/get_all
其中v1字符串拼接后被去掉了
解决办法：
直接让baseUrl已/符号结尾
NSURL *baseUrl = [NSURL URLWithString:@"http://test.com/v1/"];
NSLog(@"%@", baseUrl);
NSURL *newURL = [NSURL URLWithString:@"test/get_all" relativeToURL: baseUrl];
NSLog(@"newURL:%@",[newURL absoluteString]);//http://test.com/v1/test/get_all
34、URL编码 、解码
编码:iOS中http请求遇到汉字的时候，需要转化成UTF-8，用到的方法是：
NSString *result = [sns_info stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLPathAllowedCharacterSet]];
解码:请求后，返回的数据，如何显示的是这样的格式：%3A%2F%2F，此时需要我们进行UTF-8解码，用到的方法是：
NSString *resultData = result.stringByRemovingPercentEncoding;
35、reactiveCocoa rac_signalForControlEvents多次触发解决方法
原因：
我们知道cell在移出屏幕时并没有被销毁，而是到了一个重用池中，放到池子前我们已经做了[[cell.btn rac_signalForControlEvents:UIControlEventTouchUpInside]subscribeNext:^(idx) {}];
，取不到的话再创建。所以取出来的cell极有可能是池子里的，取出来之后再进行上述的rac_signalForControlEvents操作，导致每rac_signalForControlEvents多少次操，点击按钮时，事件就被触发多少次！
此时就得通过takeUntil:someSignal来终止cell.btn之前的signal了：
解决：
[[_cell.btn rac_signalForControlEvents:UIControlEventTouchUpInside] subscribeNext:^(__kindof UIControl * _Nullable x) {
}];
换成
[[[cell.deleteBtn rac_signalForControlEvents:UIControlEventTouchUpInside] takeUntil:cell.rac_prepareForReuseSignal] subscribeNext:^(__kindof UIControl * _Nullable x) {
}];
36、一个Label 显示两种颜色的写法
NSAttributedString *commentCountAttrString = [[NSAttributedString alloc] initWithString:@"回复：" attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14],NSForegroundColorAttributeName:CFontColor3}];
NSMutableAttributedString *commentAttrString = [[NSMutableAttributedString alloc] initWithString:_messageModel.content attributes:@{NSFontAttributeName:[UIFont boldSystemFontOfSize:14],NSForegroundColorAttributeName:CFontColor5}];
NSMutableAttributedString *commentString = [[NSMutableAttributedString alloc] init];
[commentString appendAttributedString: commentCountAttrString];
[commentString appendAttributedString: commentAttrString];
_replyLabel.attributedText = commentString;
37、解决iPhone 横屏启动界面错乱的问题
在AppDelegate中，在didFinishLaunchingWithOptions方法中创建window前先加入:
application.statusBarOrientation = UIInterfaceOrientationPortrait;
38、iPhone 屏幕亮度
//获取系统屏幕当前的亮度值
CGFloat value = [UIScreen mainScreen].brightness;
//设置系统屏幕的亮度值
[[UIScreen mainScreen] setBrightness:value];
38、如何让在UIScrollView的vc移动时也能调用生命周期？
手动调用VC的生命周期：
NSInteger currentIndex = contentOffset.x/self.frame.size.width;
UIViewController *oldVC = nil;
if (currentIndex != -1) {
oldVC = _viewsArray[currentIndex];
}
UIViewController *newsVc = _viewsArray[currentIndex];
if (newsVc.view.superview) {//调用生命周期函数(如viewwillappear等)
if (oldVC) {
[newsVc beginAppearanceTransition:NO animated:YES];
[newsVc endAppearanceTransition];
}
[newsVc beginAppearanceTransition:YES animated:YES];
[newsVc endAppearanceTransition];
}
39、常用C语言函数
一.随机数:
1.rand();
范围: 0-无穷大.
特点: 仅第一次随机,其他次都是和第一次相同.常用于调试.
返回值: long
实例: int ran = rand();
2.random();
范围: 0-无穷大.
特点: 每次都随机出现一个数字
返回值: long
二: 绝对值:
1.abs(int);
特点: 整数的绝对值
返回值: int
实例: int ab = abs(-1);
2.fabs(double);
特点: 浮点数的绝对值
返回值: double
实例: double fab = fabs(-12.345);
三: 取整
1.trunc(double);
特点: 直接取整
返回值: double
实例: double tru = trunc(3.444);
2.ceil(double)
特点: 向上取整 (舍弃小数点部分，往个位数进1）
返回值: double
实例: double ce = ceil(12.345);
3.floor(double);
特点: 向下取整 (舍弃小数点部分）
返回值: double
实例: double flo = floor(12.345);
4.四舍五入
实现方法:巧妙的利用取整规则
说明: a是要四舍五入的数,b是结果
(1)如果取整的是正数:
CGFloat a = 1.5;
int b = (int)(a + 0.5);
(2)如果取整的是负数:
CGFloat a = -1.5;
int b = (int)(a - 0.5);
5.浮点数提取整数和小数
double fraction,integer;
double number = 100000.567;
fraction = modf(number, &integer);
printf("The whole and fractional parts of %lf are %lf and %lf",number, integer, fraction);
四: 算数相关
1.pow(double, double);
特点: 求a的b次方
返回值: double
实例: double po = pow(2, 3);
2.sqrt(double)
特点: 求平方根
返回值: double
实例: double sqr = sqrt(2);
五:圆周率
M_PI == π
M_PI_2 == π/2
M_PI_4 == π/4
M_1_PI == 1/π
M_2_PI == 1/2
六.比较大小
1.MAX(1, 2); 返回最大值
2.MIN(2, 1); 返回最小值
3.ABS(-2); 返回绝对值
40、UILable 样式自定义（同一个Label展示不同颜色，字体）
//拼接字符串
NSMutableString *appendStr = [NSMutableString string];
[appendStr appendString:@"摘要："];
[appendStr appendString:_movies.editor_note];
NSMutableAttributedString *noteStr = [YYPublicTools load_attributedString:appendStr font:FFont4 color:CFontColor4 Alignment:NSTextAlignmentLeft];
NSRange redRange = NSMakeRange([[noteStr string] rangeOfString:@"摘要："].location, [[noteStr string] rangeOfString:@"摘要："].length);
//需要设置的位置
[noteStr addAttribute:NSForegroundColorAttributeName value:CFontColor3 range:redRange];
[noteStr addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:14] range:redRange];
//设置
_authorSayLabel.attributedText = noteStr;
+ (NSMutableAttributedString *)load_attributedString:(NSString *)string font:(UIFont *)font color:(UIColor *)color Alignment:(NSTextAlignment )Alignment{
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithData:[string dataUsingEncoding:NSUnicodeStringEncoding] options:@{} documentAttributes:nil error:nil];
NSMutableParagraphStyle * paragraphStyle1 = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle1 setLineSpacing:7];
[paragraphStyle1 setAlignment:Alignment];
NSDictionary *attributeDict = [NSDictionary dictionaryWithObjectsAndKeys:
font,NSFontAttributeName,
paragraphStyle1,NSParagraphStyleAttributeName,color,NSForegroundColorAttributeName,nil];
[attributedString addAttributes:attributeDict range:NSMakeRange(0, [attributedString length])];
return attributedString;
}
41、解决IQKeyboardManager在UITableviewCell中TextField或者TextView不起作用的问题。
框架本身不支持所以只能用代码解决：
1.首先在- (void)viewDidLoad中调用对键盘实现监听
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
2.然后调用通知的方法:
#pragma mark 键盘出现
-(void)keyboardWillShow:(NSNotification *)note
{
CGRect keyBoardRect=[note.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
self.tableView.contentInset = UIEdgeInsetsMake(0, 0, keyBoardRect.size.height, 0);
}
#pragma mark 键盘消失
-(void)keyboardWillHide:(NSNotification *)note
{
self.tableView.contentInset = UIEdgeInsetsZero;
}
42、去除字符串首尾空格、换行
//去除首尾空格和换行
//NSCharacterSet 多个枚举选择
NSString *content = [textView.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
43、autolayout进阶
1.Content Hugging Priority
视图抗拉伸优先级, 值越小,视图越容易被拉伸,
2. Content Compression Resistance Priority:
视图抗压缩优先级, 值越小,视图越容易被压缩,
44、pod 单独安装一个新添加的库
这将安装新项目而不更新现有的repos
pod install --no-repo-update
45、iOS-限制UILabel宽度自适应的最大宽度
_userNameLabel.preferredMaxLayoutWidth = 170 * kScaleWidth; //设置多行label最大宽度，只在 numberOfLines = 0 生效
_userNameLabel.numberOfLines = 0; //可在xib 或者 Sb设置
_userNameLabel.height = 20; // 让他固定只能一行的高度 可在xib 或者 Sb设置