objective-c - 简单简洁的桌面Cocoa NSXMLParser例子？

Question

我想查看文件的元素，当出现一个特定元素时，输出标记之间的内容。

我尝试遵循 Mac Dev 中标题为 Event Driven XML Programming 的示例，但它只是没有完成得很清楚。它说要确保我对代表进行编码，但它从未显示示例。我只想看一个简单的例子:

• 假定该文件是一个好的 xml 文件。
• 其路径是 URL(或字符串)。
• 解释了委托(delegate)与解析器交互的方式。

许多 Cocoa 教程似乎几乎都是教你绕过委托(delegate)类并创建自己的 IBAction 函数，所以我错过了我认为如何正确使用委托(delegate)的培训。在示例中不清楚我是否应该在委托(delegate)类中构建委托(delegate)，或者将它们保留在带有解析器的类中。

Answer 1

这是基于我最初为 Cut out a part of a long NSString 撰写的内容。我将 NSXMLParserDelegate 代码从该 iOS 项目复制到 OS X 项目中。它从网页中的特定对象获取文本。

.h 文件:

@interface so7576593AppDelegate : NSObject <NSApplicationDelegate, NSXMLParserDelegate> {
    NSWindow *window;
    IBOutlet NSTextField *textField;

    NSMutableString *divCharacters;
    BOOL captureCharacters; 
}

@property (assign) IBOutlet NSWindow *window;

@end

.m 文件:

#import "so7576593AppDelegate.h"

@implementation so7576593AppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    captureCharacters = NO;
    NSURL *theURL = [NSURL URLWithString:@"http://maxnerios.yolasite.com/"];
    NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:theURL];
    [parser setDelegate:self];
    [parser parse];
    [parser release];

}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict {
    if ([elementName isEqual:@"div"] && [[attributeDict objectForKey:@"id"] isEqual:@"I3_sys_txt"]) {
        captureCharacters = YES;
        divCharacters = [[NSMutableString alloc] initWithCapacity:500];
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
    if (captureCharacters) {
        //from parser:foundCharacters: docs:
        //The parser object may send the delegate several parser:foundCharacters: messages to report the characters of an element. 
        //Because string may be only part of the total character content for the current element, you should append it to the current 
        //accumulation of characters until the element changes.
        [divCharacters appendString:string];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
    if (captureCharacters) {
        captureCharacters = NO;
        [textField setStringValue:divCharacters];
        [divCharacters release];
    }
}

@end