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Diffstat (limited to 'src/qml/doc/src/qmllanguageref/documents/definetypes.qdoc')
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1 files changed, 100 insertions, 14 deletions
diff --git a/src/qml/doc/src/qmllanguageref/documents/definetypes.qdoc b/src/qml/doc/src/qmllanguageref/documents/definetypes.qdoc index 2de4eb0c18..a4119ff793 100644 --- a/src/qml/doc/src/qmllanguageref/documents/definetypes.qdoc +++ b/src/qml/doc/src/qmllanguageref/documents/definetypes.qdoc @@ -29,25 +29,37 @@ \title Defining Object Types through QML Documents \brief Description of how a QML document is a reusable type definition -One of the core features of QML is that it enables QML object types to be easily defined in a lightweight manner through QML documents to suit the needs of individual QML applications. The standard \l {Qt Quick} module provides various types like \l Rectangle, \l Text and \l Image for building a QML application; beyond these, you can easily define your own QML types to be reused within your application. This ability to create your own types forms the building blocks of any QML application. +One of the core features of QML is that it enables QML object types to be +easily defined in a lightweight manner through QML documents to suit the needs +of individual QML applications. The standard \l {Qt Quick} module provides +various types like \l Rectangle, \l Text and \l Image for building a QML +application; beyond these, you can easily define your own QML types to be +reused within your application. This ability to create your own types forms the +building blocks of any QML application. \section1 Defining an Object Type with a QML File \section2 Naming Custom QML Object Types -To create an object type, a QML document should be placed into a text file named as \e <TypeName>.qml where \e <TypeName> is the desired name of the type. The type name has the following requirements: +To create an object type, a QML document should be placed into a text file +named as \e <TypeName>.qml where \e <TypeName> is the desired name of the type. +The type name has the following requirements: \list \li It must be comprised of alphanumeric characters or underscores. \li It must begin with an uppercase letter. \endlist -This document is then automatically recognized by the engine as a definition of a QML type. Additionally, a type defined in this manner is automatically made available to other QML files within the same directory as the engine searches within the immediate directory when resolving QML type names. +This document is then automatically recognized by the engine as a definition of +a QML type. Additionally, a type defined in this manner is automatically made +available to other QML files within the same directory as the engine searches +within the immediate directory when resolving QML type names. \section2 Custom QML Type Definition -For example, below is a document that declares a \l Rectangle with a child \l MouseArea. The document has been saved to file named \c SquareButton.qml: +For example, below is a document that declares a \l Rectangle with a child \l +MouseArea. The document has been saved to file named \c SquareButton.qml: \qml // SquareButton.qml @@ -65,7 +77,10 @@ Rectangle { } \endqml -Since the file is named \c SquareButton.qml, \b {this can now be used as a type named \c SquareButton by any other QML file within the same directory}. For example, if there was a \c myapplication.qml file in the same directory, it could refer to the \c SquareButton type: +Since the file is named \c SquareButton.qml, \b {this can now be used as a type +named \c SquareButton by any other QML file within the same directory}. For +example, if there was a \c myapplication.qml file in the same directory, it +could refer to the \c SquareButton type: \qml // myapplication.qml @@ -76,23 +91,80 @@ SquareButton {} \image documents-definetypes-simple.png -This creates a 100 x 100 red \l Rectangle with an inner \l MouseArea, as defined in \c SquareButton.qml. When this \c myapplication.qml document is loaded by the engine, it loads the SquareButton.qml document as a component and instantiates it to create a \c SquareButton object. +This creates a 100 x 100 red \l Rectangle with an inner \l MouseArea, as +defined in \c SquareButton.qml. When this \c myapplication.qml document is +loaded by the engine, it loads the SquareButton.qml document as a component and +instantiates it to create a \c SquareButton object. + +The \c SquareButton type encapsulates the tree of QML objects declared in \c +SquareButton.qml. When the QML engine instantiates a \c SquareButton object +from this type, it is instantiating an object from the \l Rectangle tree +declared in \c SquareButton.qml. + +\note the letter case of the file name is significant on some (notably UNIX) +filesystems. It is recommended the file name case matches the case of the +desired QML type name exactly - for example, \c Box.qml and not \c BoX.qml - +regardless of the platform to which the QML type will be deployed. + +\section2 Inline Components + +Sometimes, it can be inconvenient to create a new file for a type, for +instance when reusing a small delegate in multiple views. If you don't actually +need to expose the type, but only need to create an instance, +\l{QtQml::Component}{Component} is an option. +But if you want to declare properties with the component types, or if you +want to use it in multiple files, \c Component is not an option. In that case, +you can use \e {inline components}. Inline components declare a new component +inside of a file. The syntax for that is +\code +component <component name> : BaseType { + // declare properties and bindings here +} +\endcode + +Inside the file which declares the inline component, the type can be referenced +simply by its name. + +\snippet qml/qml-documents/Images.qml document + +In other files, it has to be prefixed with the name of its containing component. + +\snippet qml/qml-documents/LabeledImageBox.qml document + +\note Inline components don't share their scope with the component they are +declared in. In the following example, when \c A.MyInlineComponent in file +B.qml gets created, a ReferenceError will occur, as \c root does not exist as +an id in B.qml. +It is therefore advisable not to reference objects in an inline component +which are not part of it. -The \c SquareButton type encapsulates the tree of QML objects declared in \c SquareButton.qml. When the QML engine instantiates a \c SquareButton object from this type, it is instantiating an object from the \l Rectangle tree declared in \c SquareButton.qml. +\snippet qml/qml-documents/A.qml document +\snippet qml/qml-documents/B.qml document -\note the letter case of the file name is significant on some (notably UNIX) filesystems. It is recommended the file name case matches the case of the desired QML type name exactly - for example, \c Box.qml and not \c BoX.qml - regardless of the platform to which the QML type will be deployed. +\note Inline components cannot be nested. \section2 Importing Types Defined Outside the Current Directory If \c SquareButton.qml was not in the same directory as \c myapplication.qml, -the \c SquareButton type would need to be specifically made available through an \e import statement in \c myapplication.qml. It could be imported from a relative path on the file system, or as an installed module; see \l {QML Modules}{module} for more details. +the \c SquareButton type would need to be specifically made available through +an \e import statement in \c myapplication.qml. It could be imported from a +relative path on the file system, or as an installed module; see \l {QML +Modules}{module} for more details. \section1 Accessible Attributes of Custom Types -The \b {root object} definition in a .qml file \b {defines the attributes that are available for a QML type}. All properties, signals and methods that belong to this root object - whether they are custom declared, or come from the QML type of the root object - are externally accessible and can be read and modified for objects of this type. +The \b {root object} definition in a .qml file \b {defines the attributes that +are available for a QML type}. All properties, signals and methods that belong +to this root object - whether they are custom declared, or come from the QML +type of the root object - are externally accessible and can be read and +modified for objects of this type. -For example, the root object type in the \c SquareButton.qml file above is \l Rectangle. This means any properties defined by the \l Rectangle type can be modified for a \c SquareButton object. The code below defines three \c SquareButton objects with customized values for some of the properties of the root \l Rectangle object of the \c SquareButton type: +For example, the root object type in the \c SquareButton.qml file above is \l +Rectangle. This means any properties defined by the \l Rectangle type can be +modified for a \c SquareButton object. The code below defines three \c +SquareButton objects with customized values for some of the properties of the +root \l Rectangle object of the \c SquareButton type: \qml // application.qml @@ -107,7 +179,12 @@ Column { \image documents-definetypes-attributes.png -The attributes that are accessible to objects of the custom QML type include any \l{Defining Property Attributes}{custom properties}, \l{Defining Method Attributes}{methods} and \l{Defining Signal Attributes}{signals} that have additionally been defined for an object. For example, suppose the \l Rectangle in \c SquareButton.qml had been defined as follows, with additional properties, methods and signals: +The attributes that are accessible to objects of the custom QML type include +any \l{Defining Property Attributes}{custom properties}, \l{Defining Method +Attributes}{methods} and \l{Defining Signal Attributes}{signals} that have +additionally been defined for an object. For example, suppose the \l Rectangle +in \c SquareButton.qml had been defined as follows, with additional properties, +methods and signals: \qml // SquareButton.qml @@ -136,7 +213,9 @@ Rectangle { } \endqml -Any \c SquareButton object could make use of the \c pressed property, \c buttonClicked signal and \c randomizeColor() method that have been added to the root \l Rectangle: +Any \c SquareButton object could make use of the \c pressed property, \c +buttonClicked signal and \c randomizeColor() method that have been added to the +root \l Rectangle: \qml // application.qml @@ -154,7 +233,14 @@ SquareButton { } \endqml -Note that any of the \c id values defined in \c SquareButton.qml are not accessible to \c SquareButton objects, as id values are only accessible from within the component scope in which a component is declared. The \c SquareButton object definition above cannot refer to \c mouseArea in order to refer to the \l MouseArea child, and if it had an \c id of \c root rather than \c squareButton, this would not conflict with the \c id of the same value for the root object defined in \c SquareButton.qml as the two would be declared within separate scopes. +Note that any of the \c id values defined in \c SquareButton.qml are not +accessible to \c SquareButton objects, as id values are only accessible from +within the component scope in which a component is declared. The \c +SquareButton object definition above cannot refer to \c mouseArea in order to +refer to the \l MouseArea child, and if it had an \c id of \c root rather than +\c squareButton, this would not conflict with the \c id of the same value for +the root object defined in \c SquareButton.qml as the two would be declared +within separate scopes. */ |