ComponentBuilder Class Reference

Loads and maintains a tree of Components from a ValueTree that represents them. More...

#include <juce_ComponentBuilder.h>

Inheritance diagram for ComponentBuilder:

Classes
class	ImageProvider
	This class is used when references to images need to be stored in ValueTrees. More...
class	TypeHandler
	The class is a base class for objects that manage the loading of a type of component from a ValueTree. More...

Public Member Functions
	ComponentBuilder (const ValueTree &state)
	Creates a ComponentBuilder that will use the given state.
	ComponentBuilder ()
	Creates a builder that doesn't have a state object.
	~ComponentBuilder () override
	Destructor.
Component *	getManagedComponent ()
	Returns the builder's component (creating it if necessary).
Component *	createComponent ()
	Creates and returns a new instance of the component that the ValueTree represents.
void	registerTypeHandler (TypeHandler *type)
	Adds a type handler that the builder can use when trying to load components.
TypeHandler *	getHandlerForState (const ValueTree &state) const
	Tries to find a registered type handler that can load a component from the given ValueTree.
int	getNumHandlers () const noexcept
	Returns the number of registered type handlers.
TypeHandler *	getHandler (int index) const noexcept
	Returns one of the registered type handlers.
void	registerStandardComponentTypes ()
	Registers handlers for various standard juce components.
void	setImageProvider (ImageProvider *newImageProvider) noexcept
	Gives the builder an ImageProvider object that the type handlers can use when loading images from stored references.
ImageProvider *	getImageProvider () const noexcept
	Returns the current image provider that this builder is using, or nullptr if none has been set.
void	updateChildComponents (Component &parent, const ValueTree &children)
	Updates the children of a parent component by updating them from the children of a given ValueTree.

Public Attributes
ValueTree	state
	This is the ValueTree data object that the builder is working with.

Static Public Attributes
static const Identifier	idProperty
	An identifier for the property of the ValueTrees that is used to store a unique ID for that component.

Detailed Description

Loads and maintains a tree of Components from a ValueTree that represents them.

To allow the state of a tree of components to be saved as a ValueTree and re-loaded, this class lets you register a set of type-handlers for the different components that are involved, and then uses these types to re-create a set of components from its stored state.

Essentially, to use this, you need to create a ComponentBuilder with your ValueTree, then use registerTypeHandler() to give it a set of type handlers that can cope with all the items in your tree. Then you can call getComponent() to build the component. Once you've got the component you can either take it and delete the ComponentBuilder object, or if you keep the ComponentBuilder around, it'll monitor any changes in the ValueTree and automatically update the component to reflect these changes.

Constructor & Destructor Documentation

ComponentBuilder() [1/2]

ComponentBuilder::ComponentBuilder ( const ValueTree & state )

explicit

Creates a ComponentBuilder that will use the given state.

Once you've created your builder, you should use registerTypeHandler() to register some type handlers for it, and then you can call createComponent() or getManagedComponent() to get the actual component.

ComponentBuilder() [2/2]

ComponentBuilder::ComponentBuilder

(

)

Creates a builder that doesn't have a state object.

~ComponentBuilder()

ComponentBuilder::~ComponentBuilder ( )

override

Destructor.

Member Function Documentation

getManagedComponent()

Component * ComponentBuilder::getManagedComponent

(

)

Returns the builder's component (creating it if necessary).

The first time that this method is called, the builder will attempt to create a component from the ValueTree, so you must have registered some suitable type handlers before calling this. If there's a problem and the component can't be created, this method returns nullptr.

The component that is returned is owned by this ComponentBuilder, so you can put it inside your own parent components, but don't delete it! The ComponentBuilder will delete it automatically when the builder is destroyed. If you want to get a component that you can delete yourself, call createComponent() instead.

The ComponentBuilder will update this component if any changes are made to the ValueTree, so if there's a chance that the tree might change, be careful not to keep any pointers to sub-components, as they may be changed or removed.

createComponent()

Component * ComponentBuilder::createComponent

(

)

Creates and returns a new instance of the component that the ValueTree represents.

The caller is responsible for using and deleting the object that is returned. Unlike getManagedComponent(), the component that is returned will not be updated by the builder.

registerTypeHandler()

void ComponentBuilder::registerTypeHandler

(

TypeHandler *

type

)

Adds a type handler that the builder can use when trying to load components.

See also

Drawable::registerDrawableTypeHandlers()

getHandlerForState()

TypeHandler * ComponentBuilder::getHandlerForState

(

const ValueTree &

state

)

const

Tries to find a registered type handler that can load a component from the given ValueTree.

getNumHandlers()

int ComponentBuilder::getNumHandlers ( ) const

noexcept

Returns the number of registered type handlers.

See also

getHandler, registerTypeHandler

getHandler()

TypeHandler * ComponentBuilder::getHandler ( int index ) const

noexcept

Returns one of the registered type handlers.

See also

getNumHandlers, registerTypeHandler

registerStandardComponentTypes()

void ComponentBuilder::registerStandardComponentTypes

(

)

Registers handlers for various standard juce components.

setImageProvider()

void ComponentBuilder::setImageProvider ( ImageProvider * newImageProvider )

noexcept

Gives the builder an ImageProvider object that the type handlers can use when loading images from stored references.

The object that is passed in is not owned by the builder, so the caller must delete it when it is no longer needed, but not while the builder may still be using it. To clear the image provider, just call setImageProvider (nullptr).

getImageProvider()

ImageProvider * ComponentBuilder::getImageProvider ( ) const

noexcept

Returns the current image provider that this builder is using, or nullptr if none has been set.

updateChildComponents()

void ComponentBuilder::updateChildComponents	(	Component &	parent,
		const ValueTree &	children )

Updates the children of a parent component by updating them from the children of a given ValueTree.

Member Data Documentation

state

ValueTree ComponentBuilder::state

This is the ValueTree data object that the builder is working with.

idProperty

const Identifier ComponentBuilder::idProperty

static

An identifier for the property of the ValueTrees that is used to store a unique ID for that component.

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The documentation for this class was generated from the following file:

• juce_ComponentBuilder.h