objective-c – 在iOS数据库中创建csv文件

-(NSString *)DATAFILEPath { 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,@R_675_993@,YES); 
    NSString *documentsDirectory = [paths objectATindex:0]; 
    return [documentsDirectory StringByAppendingPathComponent:@"myfile.csv"];
}

- (IBACtion)saveAsFileAction:(id)sender {    
    if (![[NSFileManager defaultManager] fileExistsAtPath:[self DATAFILEPath]]) {
        [[NSFileManager defaultManager] createFileAtPath: [self DATAFILEPath] contents:nil attributes:nil];
        NSLog(@"Route creato");        
    }

    NSString *writeString;    
    for (int i=0; i<[dataArray count]; i++) {        
        writeString = [NSString StringWithFormat:@"%@,%@,%0.2f,",[[dataArray objectATindex:i]dates],[[dataArray objectATindex:i] time],[[dataArray objectATindex:i] category],[[dataArray objectATindex:i]place],[[dataArray objectATindex:i] amount]];        
        NSLog(@"writeString :%@",writeString);        
        NSFileHandle *handle;
        handle = [NSFileHandle fileHandleForWriTingAtPath: [self DATAFILEPath] ]; 
        //say to handle where's the file fo write
        [handle truncateFileAtOffset:[handle seekToEndOfFile]]; 
        //position handle cursor to the end of file
        [handle writeData:[writeString dataUsingEncoding:NSUTF8StringEncoding]];      
    }    
}

解决方法

- (IBACtion)saveAsFileAction:(id)sender {

    if (![[NSFileManager defaultManager] fileExistsAtPath:[self DATAFILEPath]]) {
        [[NSFileManager defaultManager] createFileAtPath: [self DATAFILEPath] contents:nil attributes:nil];
        NSLog(@"Route creato");
    }

    NSMutableString *writeString = [NSMutableString StringWithCapacity:0]; //don't worry about the capacity,it will expand as necessary

    for (int i=0; i<[dataArray count]; i++) {
        writeString = [writeString appendString:[NSString StringWithFormat:@"%@,\n",[[dataArray objectATindex:i] amount]]]; //the \n will put a newline in
      }
    }

    //Moved this stuff out of the loop so that you write the complete String once and only once.
    NSLog(@"writeString :%@",writeString);

    NSFileHandle *handle;
    handle = [NSFileHandle fileHandleForWriTingAtPath: [self DATAFILEPath] ]; 
    //say to handle where's the file fo write
    [handle truncateFileAtOffset:[handle seekToEndOfFile]]; 
    //position handle cursor to the end of file
    [handle writeData:[writeString dataUsingEncoding:NSUTF8StringEncoding]];
}