The QXmlName class represents the name of an XML node, in an efficient, namespace-aware way. 更多...
The QXmlName class represents the name of an XML node, in an efficient, namespace-aware way.
QXmlName represents the name of an XML node in a way that is both efficient and safe for comparing names. Normally, an XML node represents an XML element or attribute, but QXmlName can also represent the names of other kinds of nodes, e.g., QAbstractXmlReceiver.processingInstruction () and QAbstractXmlReceiver.namespaceBinding ().
The name of an XML node has three components: The namespace URI ， local name ，和 prefix . To see what these refer to in XML, consider the following snippet.
<book xmlns:dc='http://purl.org/dc/elements/1.1'
xmlns='http://example.com/MyDefault'>
<dc:title>Mobey Dick</dc:title> ...
</book>
For the element named book , localName () 返回 book , namespaceUri () 返回 http://example.com/MyDefault ，和 prefix () returns an empty string. For the element named title , localName () 返回 title , namespaceUri () 返回 http://purl.org/dc/elements/1.1 ，和 prefix () 返回 dc .
To ensure that operations with QXmlName are efficient, e.g., copying names and comparing them, each instance of QXmlName is associated with a name pool , which must be specified at QXmlName construction time. The three components of the QXmlName, i.e., the namespace URI, the local name, and the prefix, are stored in the name pool mapped to identifiers so they can be shared. For this reason, the only way to create a valid instance of QXmlName is to use the class constructor, where the name pool , local name, namespace URI, and prefix must all be specified.
Note that QXmlName's default constructor constructs a null instance. It is typically used for allocating unused entries in collections of QXmlName.
A side effect of associating each instance of QXmlName with a name pool is that each instance of QXmlName is tied to the QXmlNamePool with which it was created. However, the QXmlName class does not keep track of the name pool, so all the accessor functions, e.g., namespaceUri (), prefix (), localName ()，和 toClarkName () require that the correct name pool be passed to them. Failure to provide the correct name pool to these accessor functions results in undefined behavior.
注意： name pool is not an XML namespace. One name pool can represent instances of QXmlName from different XML namespaces, and the instances of QXmlName from one XML namespace can be distributed over multiple name pools .
To determine what a QXmlName refers to, the namespace URI 和 local name are used. The prefix is not used because the prefix is simply a shorthand name for use in place of the normally much longer namespace URI. Nor is the prefix used in name comparisons. For example, the following two element nodes represent the same element and compare equal.
<svg xmlns="http://www.w3.org/2000/svg"/>
<x:svg xmlns:x="http://www.w3.org/2000/svg"/>
Although the second name has the prefix x , the two names compare equal as instances of QXmlName, because the prefix is not used in the comparison.
A local name can never be an empty string, although the prefix and namespace URI can. If the prefix is not empty, the namespace URI cannot be empty. Local names and prefixes must be valid NCNames , e.g., abc.def or abc123 .
QXmlName represents what is sometimes called an expanded QName , or simply a QName.
Constructs an uninitialized QXmlName . To build a valid QXmlName , you normally use the other constructor, which takes a name pool , namespace URI, local name, and prefix as parameters. But you can also use this constructor to build a null QXmlName and then assign an existing QXmlName 到它。
另请参阅 isNull ().
构造 QXmlName instance that inserts localName , namespaceURI and prefix into namePool if they aren't already there. The accessor 函数 namespaceUri (), prefix (), localName ()，和 toClarkName () must be passed the namePool used here, so the namePool must remain in scope while the accessor functions might be used. However, two instances can be compared with == or != and copied without the namePool .
The user guarantees that the string components are valid for a QName. In particular, the local name, and the prefix (if present), must be valid NCNames 。 function isNCName () can be used to test validity of these names. The namespace URI should be an absolute URI. QUrl.isRelative () can be used to test whether the namespace URI is relative or absolute. Finally, providing a prefix is not valid when no namespace URI is provided.
namePool is not copied. Nor is the reference to it retained in this instance. This constructor inserts the three strings into namePool .
转换 clarkName 成 QXmlName , inserts into namePool ，和 returns it.
A clark name is a way to present a full QName with only one string, where the namespace cannot contain braces. Here are a couple of examples:
| Clark Name | 描述 |
|---|---|
| html | The local name html , in no namespace |
| http://www.w3.org/1999/xhtml html | The local name html , in the XHTML namespace |
| http://www.w3.org/1999/xhtml my:html | The local name html , in the XHTML namespace, with the prefix my |
If the namespace contains braces, the returned value is either invalid or has undefined content.
若 clarkName is an invalid name, a default constructed QXmlName 被返回。
该函数在 Qt 4.5 引入。
另请参阅 toClarkName ().
返回 true 若 candidate 是 NCName . An NCName is a string that can be used as a name in XML and XQuery , e.g., the prefix or local name in an element or attribute, or the name of a variable.
另请参阅 Namespaces in XML 1.0 (Second Edition), [4] NCName .
返回 true，若此 QXmlName 不是 initialized with a valid combination of namespace URI , local name ，和 prefix .
A valid local name is always required. The prefix and namespace URI can be empty, but if the prefix is not empty, the namespace URI must not be empty. Local names and prefixes must be valid NCNames , e.g., abc.def or abc123 .
Returns the local name.
Note that for efficiency, the local name string is not stored in the QXmlName but in the QXmlNamePool that was passed to the constructor. Hence, that same namePool must be passed to this function, so it can be used for looking up the local name.
Returns the namespace URI.
Note that for efficiency, the namespace URI string is not stored 在 QXmlName but in the QXmlNamePool that was passed to the constructor. Hence, that same namePool must be passed to this function, so it can be used for looking up the namespace URI.
Returns the prefix.
Note that for efficiency, the prefix string is not stored in the QXmlName but in the QXmlNamePool that was passed to the constructor. Hence, that same namePool must be passed to this function, so it can be used for looking up the prefix.
Returns this QXmlName formatted as a Clark Name. For example, if the local name is html ， prefix is x , and the namespace URI is http://www.w3.org/1999/xhtml/ , then the Clark Name returned is:
{http://www.w3.org/1999/xhtml/}x:html.
If the local name is MyWidget and the namespace is empty, the Clark Name returned is:
MyWidget
Note that for efficiency, the namespace URI, local name, and prefix strings are not stored in the QXmlName but in the QXmlNamePool that was passed to the constructor. Hence, that same namePool must be passed to this function, so it can be used for looking up the three string components.
This function can be useful for debugging.
另请参阅 XML Namespaces, James Clark and fromClarkName ().