IOS開發基礎知識--碎片28

2019-11-14 17:57:43

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1：通用的weakify和strongify

/*** 強弱引用轉換，用于解決代碼塊（block）與強引用self之間的循環引用問題* 調用方式: `@weakify_self`實現弱引用轉換，`@strongify_self`實現強引用轉換** 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/*** 強弱引用轉換，用于解決代碼塊（block）與強引用對象之間的循環引用問題* 調用方式: `@weakify(object)`實現弱引用轉換，`@strongify(object)`實現強引用轉換** 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

運用（這兩個宏一定成對出現，先weak再strong）：

@weakify(self); // 定義了一個__weak的self_weak_變量 [RACObserve(self, name) subscribeNext:^(NSString *name) {     @strongify(self); // 局域定義了一個__strong的self指針指向self_weak     self.outputLabel.text = name; }];

2：objc runtime 動態增加屬性

說明：給類擴展增加了一個新屬性。通常下類擴展只允許添加方法。必須要先引入 objc/runtime.h，主要是下面兩個方法：

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

實例（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

調用代碼：

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

3:navigationController popToViewController跳轉到上上層

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

如果動畫是翻轉頁面，有可能是因為當前頁面有鍵盤，可以先把鍵盤回收后，動作就變成正常的回退動畫效果

4：App跳轉到設置

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

5:ios時間戳13位轉換

IOS的時間轉為13位時間戳//取當前時間的秒數，這邊是到秒數NSTimeInterval time = [[NSDate date] timeIntervalSince1970];//到毫秒數，則再*1000long long curTime=[[NSDate date] timeIntervalSince1970]*1000;//ios生成的時間戳是10位13時間戳轉為IOS的時間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)轉換警告Values of type 'NSInteger' should not be used as format arguments;

蘋果app支持arm64以后會有一個問題：NSInteger變成64位了，和原來的int （%d）不匹配，會報如下warning，

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

解決辦法：1、系統推薦方法   [NSString stringWithFormat:@“%ld", (long)number];2、強制轉換    [NSString stringWithFormat:@"%d", (int)number];3、[NSString stringWithFormat:@“%@", @(number)];

7：本地語言添加文件（解決一些系統自帶的Title為英語比如Cannel Done等）

1：新建文件，Resource->Strings File 命名，2：然后點擊這個.strings 右邊有個Localization->Localizeation，增加一個英語；3：到Project-Info-Localizations 然后增加Chinses(Simplified) 選擇.strings后就可以了

8:SDWebImage獲得緩存大小，并對它進行清除

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