烦人的XML读取器类中的新行和空格问题

Question

我正在使用一位博主（http://troybrant.net/blog/）编写的类，该类接受一个XML字符串并输出一个NSDictionary。它很棒...完美地工作，但是在许多元素值的开头，我得到了一些奇怪的换行符和空格配置。

我还没有找出原因。我在这里发布这个类，以便可以得到第二个人的帮助...看看是否有人注意到他使用的方法中有任何可疑之处。

//
//  XMLReader.m
//

#import "XMLReader.h"

NSString *const kXMLReaderTextNodeKey = @"text";

@interface XMLReader (Internal)

- (id)initWithError:(NSError **)error;
- (NSDictionary *)objectWithData:(NSData *)data;

@end


@implementation XMLReader

#pragma mark -
#pragma mark Public methods

+ (NSDictionary *)dictionaryForXMLData:(NSData *)data error:(NSError **)error
{
    XMLReader *reader = [[XMLReader alloc] initWithError:error];
    NSDictionary *rootDictionary = [reader objectWithData:data];
    [reader release];
    return rootDictionary;
}

+ (NSDictionary *)dictionaryForXMLString:(NSString *)string error:(NSError **)error
{
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    return [XMLReader dictionaryForXMLData:data error:error];
}

#pragma mark -
#pragma mark Parsing

- (id)initWithError:(NSError **)error
{
    if ((self = [super init]))
    {
        errorPointer = error;
    }
    return self;
}

- (void)dealloc
{
    [dictionaryStack release];
    [textInProgress release];
    [super dealloc];
}

- (NSDictionary *)objectWithData:(NSData *)data
{
    // Clear out any old data
    [dictionaryStack release];
    [textInProgress release];

    dictionaryStack = [[NSMutableArray alloc] init];
    textInProgress = [[NSMutableString alloc] init];

    // Initialize the stack with a fresh dictionary
    [dictionaryStack addObject:[NSMutableDictionary dictionary]];

    // Parse the XML
    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
    parser.delegate = self;
    BOOL success = [parser parse];

    // Return the stack's root dictionary on success
    if (success)
    {
        NSDictionary *resultDict = [dictionaryStack objectAtIndex:0];
        return resultDict;
    }

    return nil;
}

#pragma mark -
#pragma mark NSXMLParserDelegate methods

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    // Get the dictionary for the current level in the stack
    NSMutableDictionary *parentDict = [dictionaryStack lastObject];

    // Create the child dictionary for the new element, and initilaize it with the attributes
    NSMutableDictionary *childDict = [NSMutableDictionary dictionary];
    [childDict addEntriesFromDictionary:attributeDict];

    // If there's already an item for this key, it means we need to create an array
    id existingValue = [parentDict objectForKey:elementName];
    if (existingValue)
    {
        NSMutableArray *array = nil;
        if ([existingValue isKindOfClass:[NSMutableArray class]])
        {
            // The array exists, so use it
            array = (NSMutableArray *) existingValue;
        }
        else
        {
            // Create an array if it doesn't exist
            array = [NSMutableArray array];
            [array addObject:existingValue];

            // Replace the child dictionary with an array of children dictionaries
            [parentDict setObject:array forKey:elementName];
        }

        // Add the new child dictionary to the array
        [array addObject:childDict];
    }
    else
    {
        // No existing value, so update the dictionary
        [parentDict setObject:childDict forKey:elementName];
    }

    // Update the stack
    [dictionaryStack addObject:childDict];
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    // Update the parent dict with text info
    NSMutableDictionary *dictInProgress = [dictionaryStack lastObject];

    // Set the text property
    if ([textInProgress length] > 0)
    {
        [dictInProgress setObject:textInProgress forKey:kXMLReaderTextNodeKey];

        // Reset the text
        [textInProgress release];
        textInProgress = [[NSMutableString alloc] init];
    }

    // Pop the current dict
    [dictionaryStack removeLastObject];
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    // Build the text value
    [textInProgress appendString:string];
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
    // Set the error pointer to the parser's error object
    *errorPointer = parseError;
}

@end

如果这是一个让人烦恼的问题，我很抱歉（请不要出于恶意投我反对票）。我只是想弄清楚这里发生了什么，并且缺乏自己找到它的编码技能。（我是Obj-C的新手）

克利夫

解决方案：

更改此行：

[dictInProgress setObject:textInProgress forKey:kXMLReaderTextNodeKey];

从这一行开始：

[dictInProgress setObject:[textInProgress stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] forKey:kXMLReaderTextNodeKey];

- clifgriffin

---

你是一个救命恩人，非常感谢。 - Hakem Zaied

Answer 1

您可以修剪从该类中获取的值：

NSString *trimmedValue = [value stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

那会去除前导和尾随的空格。

- Amy Worrall

---

我一直在尝试类似的东西，但令人沮丧的是，我会得到这样一个值：" \n \n \n The Awesome Value"。所以我必须循环遍历直到找到该值。非常烦人。那个字符集是否能适当地处理这种情况？（如果可以，那太棒了...我一直在使用newLineCharacterSet..从未注意到这个） - clifgriffin

我认为这个字符集应该能够处理任何组合的换行和空格。试一试吧 :) - Amy Worrall