如何在iOS中异步从Documents目录中读取文件

Question

我想异步读取存储在Documents目录中的本地文件。 我的代码如下：

-(NSString *)getLogFilePath
{
    NSString *logFileNameString = logFile;
    return  [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:logFileNameString];
}


 -(NSString *)readStringFromFile
  {
  NSString *fileAtPath =  [self getLogFilePath];
  return [[NSString alloc] initWithData:[NSDataWithContentsOfFile:fileAtPath] encoding:NSUTF8StringEncoding];
  }

请有人在这方面帮助我。 提前致谢。

Answer 1

使用Grand Central Dispatch和Block语法来做到这一点，

+(void) readStringFromFileWithCompletion:(void (^)(BOOL success,NSString *output))completionBlock{


dispatch_queue_t myQueue = dispatch_queue_create("FileReadingQueue",NULL);
dispatch_async(myQueue, ^{
    // Perform long running process
    NSString *fileAtPath =  [self getLogFilePath];
    NSString *output = [[NSString alloc] initWithData:[NSData dataWithContentsOfFile:fileAtPath] encoding:NSUTF8StringEncoding];

    completionBlock(true,output);

});

}

用你的方法

[self readStringFromFileWithCompletion:^(BOOL success, NSString *output) {
    // use 'output' here, to get the string read from file
}];