IOS开发基础知识--碎片28

2019-11-14 17:57:43

字体：大中小

来源：转载

供稿：网友

1：通用的weakify和strongify

/*** 强弱引用转换，用于解决代码块（block）与强引用self之间的循环引用问题* 调用方式: `@weakify_self`实现弱引用转换，`@strongify_self`实现强引用转换** 示例：* @weakify_self* [obj block:^{* @strongify_self* self.PRoperty = something;* }];*/#ifndef    weakify_self#if __has_feature(objc_arc)#define weakify_self autoreleasepool{} __weak __typeof__(self) weakSelf = self;#else#define weakify_self autoreleasepool{} __block __typeof__(self) blockSelf = self;#endif#endif#ifndef    strongify_self#if __has_feature(objc_arc)#define strongify_self try{} @finally{} __typeof__(weakSelf) self = weakSelf;#else#define strongify_self try{} @finally{} __typeof__(blockSelf) self = blockSelf;#endif#endif/*** 强弱引用转换，用于解决代码块（block）与强引用对象之间的循环引用问题* 调用方式: `@weakify(object)`实现弱引用转换，`@strongify(object)`实现强引用转换** 示例：* @weakify(object)* [obj block:^{* @strongify(object)* strong_object = something;* }];*/#ifndef    weakify#if __has_feature(objc_arc)#define weakify(object) autoreleasepool{} __weak __typeof__(object) weak##_##object = object;#else#define weakify(object) autoreleasepool{} __block __typeof__(object) block##_##object = object;#endif#endif#ifndef    strongify#if __has_feature(objc_arc)#define strongify(object) try{} @finally{} __typeof__(object) strong##_##object = weak##_##object;#else#define strongify(object) try{} @finally{} __typeof__(object) strong##_##object = block##_##object;#endif#endif

运用（这两个宏一定成对出现，先weak再strong）：

@weakify(self); // 定义了一个__weak的self_weak_变量 [RACObserve(self, name) subscribeNext:^(NSString *name) {     @strongify(self); // 局域定义了一个__strong的self指针指向self_weak     self.outputLabel.text = name; }];

2：objc runtime 动态增加属性

说明：给类扩展增加了一个新属性。通常下类扩展只允许添加方法。必须要先引入 objc/runtime.h，主要是下面两个方法：

赋值：OBJC_EXPORT void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)获得值：OBJC_EXPORT id objc_getAssociatedObject(id object, const void *key)

实例（引用）：

UILabel+Associate.h#import <UIKit/UIKit.h>@interface UILabel (Associate)- (void) setFlashColor:(UIColor *) flashColor;- (UIColor *) getFlashColor;@endUILabel+Associate.m#import "UILabel+Associate.h"#import <objc/runtime.h>@implementation UILabel (Associate)static char flashColorKey;- (void) setFlashColor:(UIColor *) flashColor{    objc_setAssociatedObject(self, &flashColorKey, flashColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);}- (UIColor *) getFlashColor{   return objc_getAssociatedObject(self, &flashColorKey);}@end

调用代码：

    UILabel *lab = [[UILabel alloc] init];    [lab setFlashColor:[UIColor redColor]];    NSLog(@"%@", [lab getFlashColor]);

3:navigationController popToViewController跳转到上上层

        NSUInteger index=self.navigationController.viewControllers.count-3;        [self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:index] animated:YES];

如果动画是翻转页面，有可能是因为当前页面有键盘，可以先把键盘回收后，动作就变成正常的回退动画效果

4：App跳转到设置

             UIapplication *app = [UIApplication sharedApplication];             NSURL *settingsURL = [NSURL URLWithString:UIApplicationOpenSettingsURLString];             if ([app canOpenURL:settingsURL]) {                 [app openURL:settingsURL];             }

5:ios时间戳13位转换

IOS的时间转为13位时间戳//取当前时间的秒数，这边是到秒数NSTimeInterval time = [[NSDate date] timeIntervalSince1970];//到毫秒数，则再*1000long long curTime=[[NSDate date] timeIntervalSince1970]*1000;//ios生成的时间戳是10位13时间戳转为IOS的时间NSString * timeStampString = @"1423189125874";    NSDate *date = [NSDate dateWithTimeIntervalSince1970:[timeStampString doubleValue] / 1000];或者NSString * timeStampString = @"1423189125874";   NSTimeInterval _interval=[[timeStampString substringToIndex:10] doubleValue];   NSDate *date = [NSDate dateWithTimeIntervalSince1970:_interval];

6:iOS之整型(NSInteger)转换警告Values of type 'NSInteger' should not be used as format arguments;

苹果app支持arm64以后会有一个问题：NSInteger变成64位了，和原来的int （%d）不匹配，会报如下warning，

Values of type 'NSInteger' should not be used as format arguments; add an explicit cast to 'long' instead

解决办法：1、系统推荐方法   [NSString stringWithFormat:@“%ld", (long)number];2、强制转换    [NSString stringWithFormat:@"%d", (int)number];3、[NSString stringWithFormat:@“%@", @(number)];

7：本地语言添加文件（解决一些系统自带的Title为英语比如Cannel Done等）

1：新建文件，Resource->Strings File 命名，2：然后点击这个.strings 右边有个Localization->Localizeation，增加一个英语；3：到Project-Info-Localizations 然后增加Chinses(Simplified) 选择.strings后就可以了

8:SDWebImage获得缓存大小，并对它进行清除

        float tmpSize = [[SDImageCache sharedImageCache] getSize];        NSString *clearCacheName =@"当前缓存已清理";        if (tmpSize>0) {            clearCacheName=tmpSize >= 1 ? [NSString stringWithFormat:@"成功清理缓存(%.2fM)",tmpSize] : [NSString stringWithFormat:@"成功清理缓存(%.2fK)",tmpSize * 1024];        }        [[SDImageCache sharedImageCache] clearDisk];