如何使用 CHCSVParser 类 [英] How To Use the CHCSVParser class

问题描述

我正在使用 Dave DeLong 出色的 CHCSVParser 用于 Objective-C 的超长 .CSV 文件并且在使用它时遇到了一些麻烦.我会使用 arrayWithContentsOfCSVFile 方法，但我在 iPhone 上运行代码并将整个文件解析到内存中会占用比可用内存更多的内存.

I am playing around with Dave DeLong's excellent CHCSVParser for Objective-C with an extremely long .CSV file and am running into some trouble using it. I would use the arrayWithContentsOfCSVFile method, but I'm running the code on an iPhone and parsing the whole file into memory would take more memory than is available.

在我下面的代码中，解析器打开文档并完美地调用委托方法，但是在每一行之后我在哪里停止并访问数据(以创建一个 Core Data 对象并将其保存到数据存储)?我假设这将在 - (void) parser:(CHCSVParser *)parser didEndLine:(NSUInteger)lineNumber 中，但是我如何获得 NSArray(或其他)的解析器处理完行后的数据?

In my code below, the parser opens the document and calls the delegate methods perfectly, but where in the delegate do I stop after each line and access the data (to create and save a Core Data object to the data store)? I assume that would be in - (void) parser:(CHCSVParser *)parser didEndLine:(NSUInteger)lineNumber, but how do I get an NSArray (or whatever) of the data from the parser when it's done with the line?

这是我目前的代码:

//
// The code from a method in my view controller:
//
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSFileManager *manager = [NSFileManager defaultManager];
NSError *err = nil;
NSArray *fileList = [manager contentsOfDirectoryAtPath:documentsDirectory error:&err];
NSString *fileName = [fileList objectAtIndex:1];
NSURL *inputFileURL = [NSURL fileURLWithPath: [documentsDirectory stringByAppendingPathComponent:fileName]];


NSStringEncoding encoding = 0;
CHCSVParser *p = [[CHCSVParser alloc] initWithContentsOfCSVFile:[inputFileURL path] usedEncoding:&encoding error:nil];
[p setParserDelegate:self];
[p parse];
[p release];

...

#pragma mark -
#pragma mark CHCSVParserDelegate methods

- (void) parser:(CHCSVParser *)parser didStartDocument:(NSString *)csvFile {
    NSLog(@"Parser started!");
}

- (void) parser:(CHCSVParser *)parser didStartLine:(NSUInteger)lineNumber {
    //NSLog(@"Parser started line: %i", lineNumber);
}

- (void) parser:(CHCSVParser *)parser didEndLine:(NSUInteger)lineNumber {
    NSLog(@"Parser ended line: %i", lineNumber);
}

- (void) parser:(CHCSVParser *)parser didReadField:(NSString *)field {
    //NSLog(@"Parser didReadField: %@", field);
}

- (void) parser:(CHCSVParser *)parser didEndDocument:(NSString *)csvFile {
    NSLog(@"Parser ended document: %@", csvFile);
}

- (void) parser:(CHCSVParser *)parser didFailWithError:(NSError *)error {
    NSLog(@"Parser failed with error: %@ %@", [error localizedDescription], [error userInfo]);
}

谢谢！

推荐答案

我很高兴看到我的代码被证明是有用的！:)

I'm glad to see that my code is proving useful! :)

CHCSVParser 在行为上与 NSXMLParser 相似，因为它每次发现有趣的东西时，都会通过其中一个委托回调通知您.但是，如果您选择忽略它在回调中提供给您的数据，那么它就消失了.这些解析器(CHCSVParser 和 NSXMLParser)非常愚蠢.他们只知道他们试图解析的内容的格式，但除此之外并没有做太多事情.

CHCSVParser is similar in behavior to an NSXMLParser, in that every time it finds something interesting, it's going to let you know via one of the delegate callbacks. However, if you choose to ignore the data that it gives you in the callback, then it's gone. These parsers (CHCSVParser and NSXMLParser) are pretty stupid. They just know the format of the stuff they're trying to parse, but don't really do much beyond that.

因此，简而言之，答案是您必须自己保存它".如果您查看 NSArray 类别的代码，您将在 .m 文件中看到它正在使用 一个简单的 NSObject 子类作为解析器委托，该子类将字段聚合到一个数组中，然后添加该数组到整个数组.你需要做类似的事情.

So the answer, in a nutshell, is "you have to save it yourself". If you look at the code for the NSArray category, you'll see in the .m file that it's using a simple NSObject subclass as the parser delegate, and that subclass is what's aggregating the fields into an array, and then adding that array to the overall array. You'll need to do something similar.

示例委托:

@interface CSVParserDelegate : NSObject <CHCSVParserDelegate> {
  NSMutableArray * currentRow;
}
@end

@implementation CSVParserDelegate

- (void) parser:(CHCSVParser *)parser didStartLine:(NSUInteger)lineNumber {
  currentRow = [[NSMutableArray alloc] init];
}
- (void) parser:(CHCSVParser *)parser didReadField:(NSString *)field {
  [currentRow addObject:field];
}
- (void) parser:(CHCSVParser *)parser didEndLine:(NSUInteger)lineNumber {
  NSLog(@"finished line! %@", currentRow);
  [self doSomethingWithLine:currentRow];
  [currentRow release], currentRow = nil;
}
@end

但是，我可以说服我修改解析器的行为来聚合行本身，但是如果我沿着这条路线走，为什么不让解析器聚合整个文件呢?(答案:不应该)

However, I could be convinced to modify the behavior of the parser to aggregate the row itself, but if I go down that route, why not just have the parser aggregate the entire file? (Answer: it shouldn't)

这篇关于如何使用 CHCSVParser 类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！