iOS开发常用细节

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
    // 处理各种耗时间的事情，比如网络请求数据，天知道要什么时候才能结束

    dispatch_async(dispatch_get_main_queue(), ^(void) {

        // 好了以后，我们回到主线程进行界面刷新
    });
});

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{

});

double delaySeconds = 5.0;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delaySeconds * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

});

dispatch_queue_t kent_queue = dispatch_queue_create("kent.com", NULL);

dispatch_async(kent_queue, ^{
    NSLog(@"开启异步任务");
});

dispatch_sync(kent_queue, ^{
    NSLog(@"开启同步任务");
});



//----------------------------------

//执行10次，每次执行都开新进程，所以顺序不一定
dispatch_apply(10, DISPATCH_QUEUE_PRIORITY_DEFAULT, ^(size_t index) {
    NSLog(@"index = %ld",index);
}); 

/-----------------------------------

// 多个任务（在多个线程）同时执行，等他们完成以后，再执行其他任务
//先建立一个分组，多个任务形成一个组，在组里面的任务完成以后再执行后续的任务

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_group_t group = dispatch_group_create();

dispatch_group_async(group, queue, ^{
    NSLog(@"1");
});
dispatch_group_async(group, queue, ^{
    NSLog(@"2");
});
dispatch_group_async(group, queue, ^{
    NSLog(@"3");
});
dispatch_group_async(group, queue, ^{
    NSLog(@"4");
});
dispatch_group_async(group, queue, ^{
    NSLog(@"5");
});

dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    NSLog(@"主线程");
});

//获取根目录
NSString *homePath = NSHomeDirectory();
NSLog(@"Home目录：%@",homePath);

//获取Documents文件夹目录
NSArray *docPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsPath = [docPath objectAtIndex:0];
NSLog(@"Documents目录：%@",documentsPath);

//获取Cache目录
NSArray *cacPath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *cachePath = [cacPath objectAtIndex:0];
NSLog(@"Cache目录：%@",cachePath);   

//获取Library目录
NSArray *libsPath = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *libPath = [libsPath objectAtIndex:0];
NSLog(@"Library目录：%@",libPath);

//获取temp目录
NSString *tempPath = NSTemporaryDirectory();
NSLog(@"temp目录：%@",tempPath);

NSArray *testArray1 = @[@"1",@"2"];
//documentsPath是前面创建的
NSString *filePath = [documentsPath stringByAppendingPathComponent:@"testArray1.text"];
//写入
[testArray1 writeToFile:filePath atomically:YES];
//读取
NSArray *readTestArray1 = [NSArray arrayWithContentsOfFile:filePath];

//获取文件管理器
NSFileManager *fileManager = [NSFileManager defaultManager];

//文件目录名
NSString *testDirectory = [documentsPath stringByAppendingPathComponent:@"ttttest"];

//执行创建
[fileManager createDirectoryAtPath:testDirectory withIntermediateDirectories:YES attributes:nil error:nil];   

//在文件目录下继续写入的路径
NSString *tPath = [testDirectory stringByAppendingPathComponent:@"t1.txt"];

//要写入内容
NSString *contentString = @"ready...";

//执行写入
[fileManager createFileAtPath:tPath contents:[contentString dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];

//获取documents下面的所有文件，可以看到隐藏的内容
NSArray *file = [fileManager subpathsOfDirectoryAtPath:documentsPath error:nil];

NSLog(@"file%@",file);

NSArray *file2 = [fileManager subpathsAtPath:documentsPath];

NSLog(@"file2=%@",file2);  

//移到准备操作的目录下
[fileManager changeCurrentDirectoryPath:[documentsPath stringByExpandingTildeInPath]];

//创建文件
NSString *fileName = @"newTest.txt";

NSString *tString = @"ttttttt";

[fileManager createFileAtPath:fileName contents:[tString dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];