-(void)removeFileByPath:(NSString*)path{
    NSFileManager *fm = [NSFileManager defaultManager];
    if (![fm fileExistsAtPath:path]) {
        NSLog(@"no file");
        return;
    }
    NSError *error=nil;
    [fm removeItemAtPath:path error:&error];
    if (error!=nil) {//failed
        NSLog(@"failed to remove %@",[error localizedDescription]);
    }else{
        NSLog(@"Successfully removed:%@",path);
    }
}
NSString* path=[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
path=[path stringByAppendingPathComponent:@"test.png"];
[self removeFileByPath:path];