解析嵌套的XML Objective C- NSXMLParser

Question

全,

我有以下格式的XML：

<linked-list>
    <Description>
        <desc></desc>
        <IP></IP>
    </Description>
</linked-list>

语句的内部可以有无限多个。

我应该如何使用NSXMLParser来解析它？我当前的代码如下所示，但它不能正确解析。

@implementation XMLParser

@synthesize response;

- (XMLParser *) initXMLParser
{
    self = [super init];
    // init dictionary of response data 
    response = [[NSMutableDictionary alloc] init];
    return self;
}

//Gets Start Element of SessionData
- (void)parser:(NSXMLParser *)parser 
        didStartElement:(NSString *)elementName 
        namespaceURI:(NSString *)namespaceURI 
        qualifiedName:(NSString *)qualifiedName 
        attributes:(NSDictionary *)attributeDict 
{
    if ([elementName isEqualToString:@"linked-list"])
    {
        NSLog(@"Found linked-list in the return XML! Continuing...");
        //response is a NSMutableArray instance variable

        //THIS SHOULD NEVER NEED TO BE USED
        if (!response)//if array is empty, it makes it!
        {
            NSLog(@"Dictionary is empty for some reason, creating...");
            response = [[NSMutableDictionary alloc] init];
        }
        //END: THIS SHOULD NEVER BE USED
        return;
    }
    else
    {
        currentElementName = elementName;
        NSLog(@"Current Element Name = %@", currentElementName);
        return;
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string 
{
    if (!currentElementValue) {
        // init the ad hoc string with the value     
        currentElementValue = [[NSMutableString alloc] initWithString:string];
    } else {
        [currentElementValue setString:string];
        NSLog(@"Processing value for : %@", string);
    }
}  

//Gets End Element of linked-list
- (void)parser:(NSXMLParser *)parser 
 didEndElement:(NSString *)elementName
  namespaceURI:(NSString *)namespaceURI 
 qualifiedName:(NSString *)qName {
    if ([elementName isEqualToString:@"linked-list"])
    {
        // We reached the end of the XML document
        // dumps dictionary into log
        NSLog(@"Dump:%@", [response description]);
        return;
    }
    else
    {
        //Adds key and object to dictionary
        [response setObject:currentElementValue forKey:currentElementName];
        NSLog(@"Set values, going around again... brb.");
    }
    currentElementValue = nil;
    currentElementName = nil;
}


@end

Answer 1

一些观察结果：

1. WHAT内部的无限数量的WHAT？
2. 假设可以有多个Description元素，则存储内容的外部数据结构必须是NSMutableArray而不是字典。然后，您在didStartElement:中为每个Description element.
3. Consequently，使用一个可变字典，检查元素名称是否为@"Description"，如果是，则创建一个新的NSMutableDictionary实例，并将其存储在一个ivar.
4. 中。在foundCharacters:中，您总是必须将新字符附加到现有的currentElementValue中，因为该方法可以为每个元素的内容调用多次。我看到许多人这样做是错误的，尽管苹果的示例代码清楚地展示了正确的方法。
5. In didEndElement:，这样做：

- If the element name is `@"desc"` or `@"IP"`, assign `currentElementValue` to the corresponding key in your current mutable dictionary. Don't forget to release `currentElementValue` before you set it to `nil`. You currently have a memory leak in your code because you're not doing that.
- If the element name is `@"Description"`, add the current mutable dictionary to the mutable array. Release the dictionary and set the ivar to `nil`. A new dictionary will be created the next time you encounter a `@"Description"` element in `didStartElement:`.
- If the element name is `@"linked-list"`, the mutable array will contain all the dictionaries and you're done.

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