Class Viewer | Unreal Engine 4.27 Documentation

The Class Viewer allows the user to examine a hierarchical list of classes used by the editor. Through the tool, Blueprints can be created and opened for modification. You can also open associated C++ Header files or create new C++ classes based on the selected class.

Opening the Class Viewer

The Class Viewer can be opened from the Window -> Developer Tools -> Class Viewer option.

Class Viewer Interface

The Class Viewer is comprised of three areas:

Menu Bar

Filters

Actors Only - Filters the tree to show only children of the Actor class.
Placeable Only - Filters the tree to show only placeable Actor classes.
Blueprint Bases Only - Filters the tree to show only Blueprint Bases, which Blueprints can be created from.

View

Expand All - Expands the entire tree, revealing all children.
Collapse All - Collapses the entire tree, hiding all children.

Search

The search bar allows for filtering classes by name. When a single word is searched, items only need a partial match to pass and will be highlighted. Items that fail the filter will be grayed out if they have children that pass and removed entirely if not.

Multiple words will allow a partial match on any to pass the filter. Highlighting is not available with multiple search terms.

Class Tree

This area shows the parent-child relationship between classes that pass both filters and search. Each item can be broken down into two pieces.

Class Name

This is the name of the class. Items colored in blue are Blueprint classes and white items are non-Blueprint classes.

Context Menu

The context menu is opened by clicking on Context Menu Button or by right-clicking on a Blueprint or code class. Classes must be loaded (right-click) to display a to bring up the context menu. The options available in the context menu depend on the type of class selected:

Class Type	Options	Description
Blueprint Class	[REGION:plain_list] Create Blueprint... Edit Blueprint... Find In Content Browser [/REGION]	[REGION:plain_list] Creates a new Blueprint parented to the selected Blueprint. Opens the selected Blueprint in the Blueprint Editor. Finds the Blueprint Actor in the Content Browser. [/REGION]
Code Class	[REGION:plain_list] Create Blueprint... Open C++ Header File... Create New C++ Class... [/REGION]	[REGION:plain_list] Creates a new Blueprint parented to the selected Blueprint. Opens up the class header file in Visual Studio. Opens the C++ Class Wizard to create a new class with the selected class as the Parent class. [/REGION]

Drag & Dropping

Dropping a Blueprint class Actor into a viewport will add the Actor to the scene. When successfully dragging a Class, the mouse will show what class is in hand. Only one class can be dragged at a time.

The mouse informs what class is being dragged.

Besides dropping into the viewport, classes can be dropped into combo boxes in the details window. Only classes that are children of the class associated with the combo box may be successfully dropped. An example is the World Properties details window and the GameMode Override where dropping any child class of GameMode will work.

Classes that have not been loaded will not appear in the combo box. Dropping a class into the combo box will force load the class.

Utilizing the Class Picker

The Class Picker is a mode that the Class Viewer can be switched to using only code. It is used for displaying a list of available classes such as for converting Static Meshes or selecting a parent for a new Blueprint. There are a number of ways to configure a Class Picker to show the desired results.

When putting a Class Viewer or Class Picker into a location, make sure its height is limited in some manner. Thousands of classes may be in the Viewer/Picker and unconstrained it will stretch off the screen trying to render all of them. It will automatically display a scrollbar if all items cannot be displayed in the available area.

Class Picker Options

FClassViewerInitializationOptions, which is used for initializing a Class Picker, has a number of important options to take note of to utilize the Class Picker to its fullest.

Mode - Two options for this: ClassPicker and ClassBrowsing. It is set to ClassPicker by default, ClassBrowsing will spawn what amounts to a normal Class Viewer. Most options do not function in a Class Viewer.
DisplayMode - Two options for this: TreeView and ListView. The tree will show parent-child relationships between classes while the list is a simple list of displayed classes.

General Filters

bIsActorsOnly - Will limit the classes displayed to being children of AActor.
bIsPlaceableOnly - Will limit the classes displayed to being placeable in the game world. bIsActorsOnly will be assumed true if this value is true.
bIsBlueprintBaseOnly - Will limit the classes displayed to Blueprint bases.
bShowUnloadedBlueprints - Will show unloaded Blueprints despite their parents being filtered out due to custom filters.
bShowNoneOption - Will display a "None" option in a Class Picker, does nothing with a Class Viewer. When an item is picked, a NULL class is passed.

bIsBlueprintBaseOnly is useful for limiting the list to classes that Blueprints can be created from.