iOS基础开发技巧2

这里主要讲一些我在日常开发中用到的一些小的技巧，其实也算不上技巧吧，就是省去一些不必要的代码，或者有的小问题困扰你很久说不行在这里你能找到答案

在UIView的扩展快速修改frame

在iOS修改view的frame，我们经常需要写一大堆代码，来修改frame中的一个小属性，这里有一个方法，就是直接修改frame的每个值

新建一个category UIView+PPSFrame.h

#import <UIKit/UIKit.h>

@interface UIView (PPSFrame)

@property (assign, nonatomic) CGFloat top;//上相当于frame.origin.y

@property (assign, nonatomic) CGFloat bottom;//下相当于frame.size.height + frame.origin.y

@property (assign, nonatomic) CGFloat left;//相当于frame.origin.x

@property (assign, nonatomic) CGFloat right;//相当于frame.origin.x+frame.size.width

@property (assign, nonatomic) CGFloat centerX;

@property (assign, nonatomic) CGFloat centerY;

@property (assign, nonatomic) CGFloat width;

@property (assign, nonatomic) CGFloat height;

@property (assign, nonatomic) CGSize size;

@end

在.m文件中设置各个属性

#import "UIView+Layout.h"

@implementation UIView (Layout)

@dynamic top;

@dynamic bottom;

@dynamic left;

@dynamic right;

@dynamic width;

@dynamic height;

@dynamic size;

- (CGFloat)top

{

return self.frame.origin.y;

}

- (void)setTop:(CGFloat)top

{

CGRect frame = self.frame;

frame.origin.y = top;

self.frame = frame;

}

- (CGFloat)left

{

return self.frame.origin.x;

}

- (void)setLeft:(CGFloat)left

{

CGRect frame = self.frame;

frame.origin.x = left;

self.frame = frame;

}

- (CGFloat)bottom

{

return self.frame.size.height + self.frame.origin.y;

}

- (void)setBottom:(CGFloat)bottom

{

CGRect frame = self.frame;

frame.origin.y = bottom - frame.size.height;

self.frame = frame;

}

- (CGFloat)right

{

return self.frame.size.width + self.frame.origin.x;

}

- (void)setRight:(CGFloat)right

{

CGRect frame = self.frame;

frame.origin.x = right - frame.size.width;

self.frame = frame;

}

- (CGFloat)centerX

{

return self.center.x;

}

- (void)setCenterX:(CGFloat)centerX

{

CGPoint center = self.center;

center.x = centerX;

self.center = center;

}

- (CGFloat)centerY

{

return self.center.y;

}

- (void)setCenterY:(CGFloat)centerY

{

CGPoint center = self.center;

center.y = centerY;

self.center = center;

}

- (CGFloat)width

{

return self.frame.size.width;

}

- (void)setWidth:(CGFloat)width

{

CGRect frame = self.frame;

frame.size.width = width;

self.frame = frame;

}

- (CGFloat)height

{

return self.frame.size.height;

}

- (void)setHeight:(CGFloat)height

{

CGRect frame = self.frame;

frame.size.height = height;

self.frame = frame;

}

- (CGSize)size

{

return self.frame.size;

}

- (void)setSize:(CGSize)size

{

CGRect frame = self.frame;

frame.size = size;

self.frame = frame;

}

@end

iOS OC项目的pch文件使用

在项目中如果我们需要一些公共的引用，或者一些全局的宏那我们经常在pch中设置好

具体怎么设置呢在项目下新建一个pch文件

一般我会取名项目名-PrefixHeader

在target——>Bulid Setting 中设置 PrefixHeader

我的项目文件夹结构

$(SRCROOT)这个是指工程的根目录

找到这个pch文件就行然后启动APP就会编译这个文件了

pch.h中

// APP-1-PrefixHeader.pch

// APP-1

// Created by 羊谦 on 2016/10/28.

#ifndef APP_1_PrefixHeader_pch

#define APP_1_PrefixHeader_pch

//在这里直接定义你的宏变量或者公共引用就行

#endif /* APP_1_PrefixHeader_pch */

UITableView的Group样式下顶部空白处理

要给tableHeaderView赋一个高度不为0的view才能处理顶部留白

//分组列表头部空白处理

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 0, 0.1)];

self.tableView.tableHeaderView = view;

获取某个view的Controller

其实就是根据view的响应链，来查找viewcontroller

- (UIViewController *)viewController

{

UIViewController *viewController = nil;

UIResponder *next = self.nextResponder;

while (next)

{

if ([next isKindOfClass:[UIViewController class]])

{

viewController = (UIViewController *)next;

break;

}

next = next.nextResponder;

}

return viewController;

}

清空NSUserDefaults的记录

方法一：是获取当前的app的bundleId NSUserDefaults中有方法根据bundleId清空记录

NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];

[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];

方法二：获取所有存储在NSUserDefaults中的数据，因为是按照key-value形式存储，所以循环key就能够删除数据

- (void)clearDefaults{

NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];

NSDictionary * dict = [defs dictionaryRepresentation];

for (id key in dict)

{

[defs removeObjectForKey:key];

}

[defs synchronize];

}

GCD timer定时器的使用

这里的定时器，是一个每秒在主线程跑的一个方法

__block int countSecond = 30; //倒计时

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);

dispatch_source_set_timer(timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行

dispatch_source_set_event_handler(timer, ^{

if (countSecond==0) { //倒计时完毕

//@"倒计时结束，关闭"

dispatch_source_cancel(timer);

dispatch_async(dispatch_get_main_queue(), ^{

//倒计时完毕需要执行的操作

});

}else{ //倒计时

NSLog(@"%@", [NSString stringWithFormat:@"%ld",(long)countSecond]);

dispatch_async(dispatch_get_main_queue(), ^{

//每秒需要执行的操作

//在这里更新UI之类的

});

countSecond--;

}

});

dispatch_resume(timer);

计算文件大小

- (long long)fileSizeAtPath:(NSString *)path

{

NSFileManager *fileManager = [NSFileManager defaultManager];

if ([fileManager fileExistsAtPath:path])

{

long long size = [fileManager attributesOfItemAtPath:path error:nil].fileSize;

return size;

}

return 0;

}

计算文件夹大小

- (long long)folderSizeAtPath:(NSString *)path

{

NSFileManager *fileManager = [NSFileManager defaultManager];

long long folderSize = 0;

if ([fileManager fileExistsAtPath:path])

{

NSArray *childerFiles = [fileManager subpathsAtPath:path];

for (NSString *fileName in childerFiles)

{

NSString *fileAbsolutePath = [path stringByAppendingPathComponent:fileName];

if ([fileManager fileExistsAtPath:fileAbsolutePath])

{

long long size = [fileManager attributesOfItemAtPath:fileAbsolutePath error:nil].fileSize;

folderSize += size;

}

return folderSize;

}

向上取整和向下取整

floor(x)函数，是一个向下取整函数，是一个C函数即是去不大于x的一个最大整数

floor(3.12) = 3 floor(4.9) = 4

与floor(x)函数对应的是ceil函数

这个即是向上取整了

ceil(3.9) = 4 ceil(1.2) = 2

给任何一个view设置一张图片

UIImage *image = [UIImage imageNamed:@"image"];

self.MYView.layer.contents = (__bridge id _Nullable)(image.CGImage);

self.MYView.layer.contentsRect = CGRectMake(0, 0, 0.5, 0.5);