iOS在文件末尾记录内容

-(NSString*)infoFilePath

{
NSArray *Paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES );
NSString *MyDocpath=[Paths objectAtIndex:0];
NSString *filename=[MyDocpath stringByAppendingPathComponent:[NSString stringWithFormat:@"infoFile"]];
return filename;
}

-(NSString *)currentTime{
NSDate *currentDate = [NSDate date];
NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
[dateformatter setDateFormat:@"YYYY-MM-dd mm:ss"];
NSString *currentString=[dateformatter stringFromDate:currentDate];
return currentString;
}

-(void)allWriteToFileWithL