Question

我需要一点帮助，我有一个搜索字段和按钮来触发这个方法，但我在下面得到了错误。

- (IBAction)fetchTracks:(id)sender {

NSString *input = [searchField stringValue];
NSString *searchString = [input stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog(@"searchString: %@", searchString);

NSError *error;
NSString* libraryPath = [[NSString alloc] initWithString:@"~/Music/iTunes/iTunes Music Library.xml"];
NSURL *url = [NSURL URLWithString:libraryPath];

[doc release];
doc = [[NSXMLDocument alloc] initWithContentsOfURL:url options:0 error:&error];

NSLog(@"doc: %@", doc);

[itemNodes release];
itemNodes = [[doc nodesForXPath:@"ItemSearchResponse/Items/Item" error:&error] retain];

[tableView reloadData];
}

*-[NSXMLDocument initWithContentsOfURL:选项：错误：]：无参数

有人能帮忙吗，谢谢，萨米。

Answer 1

您需要转义代码中的空格。例如，像这样

  libraryPath = [libraryPath stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];

When I add this, your code doesn t crash.
But generally, I would recommend accessing files as files (e.g. NSString stringWithContentsOfFile). It will make your life easier.

您可以看到URL不能包含的字符列表此处：

不安全：

Characters can be unsafe for a number of reasons. The space character is unsafe because significant spaces may disappear and insignificant spaces may be introduced when URLs are transcribed or typeset or subjected to the treatment of word-processing programs.

Answer 2

更改此行：

NSError *error;

对此：

NSError *error = nil;

请阅读此问题，了解为什么这样做有效的更多详细信息：NSError：使用nil检测错误实际上会关闭错误报告吗

但是，您似乎根本不关心error对象，所以最好这样调用这些方法（将&；error替换为NULL）

doc = [[NSXMLDocument alloc] initWithContentsOfURL:url options:0 error:NULL];
...
itemNodes = [[doc nodesForXPath:@"ItemSearchResponse/Items/Item" error:NULL] retain];

Answer 3

我认为您可能需要：

NSString *urlString = [@"~/Music/iTunes/iTunes Music Library.xml" stringByExpandingTildeInPath];
NSString* libraryPath = [[NSString alloc] initWithString:urlString];

友情链接