IOS－写文件到本地

-(void)writeToFileWithString:(NSString*)string withFileName:(NSString*)fileName{
   //@"Map_Succ.txt"
    NSString* fileName1 = [self filePath:fileName];
    NSFileManager* fileManager = [NSFileManager defaultManager];
    NSString* str = nil;
    if ( [fileManager fileExistsAtPath:fileName1]) {

        NSData* data = [NSData dataWithContentsOfFile:fileName1];
        str =[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        string = [NSString stringWithFormat:@"%@\n%@",str,string];

    }

    [fileManager createFileAtPath:fileName1 contents:[ string dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];

}

- (NSString*)filePath:(NSString*)fileName {
    NSArray* myPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString* myDocPath = [myPaths objectAtIndex:0];
    NSString* filePath = [myDocPath stringByAppendingPathComponent:fileName];
    return filePath;
}