根据url地址下载文件到本地，返回本地文件地址

-(NSString*)DownloadTextFile:(NSString*)fileUrl   fileName:(NSString*)_fileName
{
    NSString *sandboxPath = NSHomeDirectory();
    NSString *documentPath = [sandboxPath  stringByAppendingPathComponent:@"Documents"];//将Documents添加到sandbox路径上
    NSString *FileName=[documentPath stringByAppendingPathComponent:_fileName];//fileName就是保存文件的文件名
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if ([fileManager fileExistsAtPath:FileName])
    {
        return FileName;
    }else
    {
        NSURL *url = [NSURL URLWithString:fileUrl];
        NSLog(fileUrl);
        NSData *data = [NSData dataWithContentsOfURL:url];
       [data writeToFile:FileName atomically:YES];//将NSData类型对象data写入文件，文件名为FileName
    }
    return FileName;
}

 NSString *FileName = @"myWebURL.plist";
    NSArray *cachePath= NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
    NSString *cacheDir = [cachePath objectAtIndex:0];
    NSString *FilePath = [cacheDir stringByAppendingPathComponent:FileName];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    // Copy the  file from the resourcepath to the documentpath
    if (![fileManager fileExistsAtPath:FilePath])
    {
        NSString *filePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:FileName];
        NSError *error;
        [fileManager copyItemAtPath:filePathFromApp toPath:FilePath error:&error];
    }
    NSLog(FilePath);