JUCE: ComponentBuilder Class Reference

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ComponentBuilder Class Reference
juce_gui_basics » layout

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.

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

- juce_ComponentBuilder.h