17

我想将数据从 sql 文件写入 csv 文件。我已从数组中的 sql 文件收集所有数据，并使用 for 循环将数据附加并写入 .csv 文件。但似乎它仅在一行中显示数据，它不会转到新行来创建新行。我用这个作为参考。这是我的代码：

-(NSString *)dataFilePath { 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, 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]];      
    }    
}
4

4 回答 4

37

这只会写一行，因为每次执行循环时都会重写文件。最好writeData在循环完成之前不要在文件上。我也会像这样使用 NSMutableString：

- (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:@"%@, %@, %@, %@, %0.2f, \n",[[dataArray objectAtIndex:i]dates],[[dataArray objectAtIndex:i] time],[[dataArray objectAtIndex:i] category],[[dataArray objectAtIndex:i]place],[[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]];
}
于 2012-04-12T07:20:48.633 回答
5 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES); 
    NSString *documentsDir = [paths objectAtIndex:0];
    NSString *root = [documentsDir stringByAppendingPathComponent:@"customers.csv"];

    NSString *temp;

    temp = [NSString stringWithFormat:@"%@", [arrCustomersName objectAtIndex:0]];

    for (int i = 1; i < [arrCustomersName count]; i++) {

        temp = [temp stringByAppendingFormat:@", %@", [arrCustomersName objectAtIndex:i]];
    }

    [temp writeToFile:root atomically:YES encoding:NSUTF8StringEncoding error:NULL];
于 2013-03-26T13:07:34.537 回答
2

试试这个它对我有用，

如果有人想在swift 3中创建 .csv 文件

   // MARK: CSV file creating
    func creatCSV() -> Void {

    let fileName = "Tasks.csv"

    let path = NSURL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(fileName)
    var csvText = "Date,Task Name,Time Started,Time Ended\n"

    for task in taskArr {
        let newLine = "\(task.date),\(task.name),\(task.startTime),\(task.endTime)\n"
        csvText.append(newLine)
    }

    do {
        try csvText.write(to: path!, atomically: true, encoding: String.Encoding.utf8)
    } catch {
        print("Failed to create file")
        print("\(error)")
    }
    print(path ?? "not found")
   }
  }

有关更多详细信息，您可以参考详细答案

希望这对某人有所帮助。

于 2017-08-31T13:05:57.350 回答
1 
 // For CSV File :
       NSMutableString *stringToWrite = [[NSMutableString alloc] init];
 [stringToWrite appendString:[NSString stringWithFormat:@"First Name,Last Name,Full Name,Phone Number, Email,Job, organizationName,Note\n\n"]];
 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
      for(int i = 0 ;i<[Contact count];i++)     {
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact objectAtIndex:i] valueForKey:@"firstName"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact objectAtIndex:i] valueForKey:@"lastName"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact valueForKey:@"userName"] objectAtIndex:i]]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact objectAtIndex:i] valueForKey:@"phoneNumber"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact objectAtIndex:i] valueForKey:@"emailAddress"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact objectAtIndex:i] valueForKey:@"jobTitle"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@,",[[Contact  objectAtIndex:i] valueForKey:@"organizationName"] ]];
           [stringToWrite appendString:[NSString stringWithFormat:@"%@\n",[[Contact objectAtIndex:i] valueForKey:@"note"] ]];
      }
      dispatch_async(dispatch_get_main_queue(), ^(void) {
           NSArray *paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
           NSString *documentDirectory=[paths objectAtIndex:0];
           NSString *strBackupFileLocation = [NSString stringWithFormat:@"%@/%@", documentDirectory,@"ContactList.csv"];
           [stringToWrite writeToFile:strBackupFileLocation atomically:YES encoding:NSUTF8StringEncoding error:nil];
      });
 });
于 2016-12-29T12:46:47.937 回答