- Create a new StaticMeshActor class called Tree using the editor.<\/li>
- Insert the following code above the class declaration:<\/li><\/ol>\n\n\n\n
#pragma once
#include \"CoreMinimal.h\"
#include \"Engine\/StaticMeshActor.h\"
#include \"Tree.generated.h\"
UENUM(BlueprintType)<\/strong>
enum TreeType<\/strong>
{<\/strong>
Tree_Poplar,<\/strong>
Tree_Spruce,<\/strong>
Tree_Eucalyptus,<\/strong>
Tree_Redwood<\/strong>
};<\/strong>
UCLASS()
class CHAPTER_09_API ATree : public AStaticMeshActor
{<\/pre>\n\n\n\n- Add the following to the Tree class:<\/li><\/ol>\n\n\n\n
UCLASS()
class CHAPTER_09_API ATree : public AStaticMeshActor
{
GENERATED_BODY()
public:<\/strong>
\/\/ Sets default values for this actor's properties<\/strong>
ATree();<\/strong>
UPROPERTY(BlueprintReadWrite)<\/strong>
TEnumAsByte<TreeType> Type;<\/strong>
};<\/pre>\n\n\n\n- Add the following to the Tree constructor:<\/li><\/ol>\n\n\n\n
#include \"Tree.h\"
#include \"ConstructorHelpers.h\"<\/strong>
\/\/ Sets default values<\/strong>
ATree::ATree()<\/strong>
{<\/strong>
\/\/ Set this actor to call Tick() every frame. You can turn
\/\/ this off to improve performance if you don't need it.<\/strong>
PrimaryActorTick.bCanEverTick = true;<\/strong>
auto MeshAsset = ConstructorHelpers::FObjectFinder<UStaticMesh>
(TEXT(\"StaticMesh'\/Engine\/BasicShapes\/Cylinder.Cylinder'\"));<\/strong>
UStaticMeshComponent * SM = GetStaticMeshComponent();<\/strong>
if (SM != nullptr)<\/strong>
{<\/strong>
if (MeshAsset.Object != nullptr)<\/strong>
{<\/strong>
SM->SetStaticMesh(MeshAsset.Object);<\/strong>
SM->SetGenerateOverlapEvents(true);<\/strong>
}<\/strong>
SM->SetMobility(EComponentMobility::Movable);<\/strong>
}<\/strong>
}<\/strong>
<\/pre>\n\n\n\n- Return to the Unreal Editor and compile your code.<\/li>
- Create a new Blueprint class called MyTree, based on Tree, by right-clicking on the Tree object and selecting Create Blueprint class based on Tree. Once the menu comes up, click on the Create Blueprint Class button.<\/li>
- Inside the blueprint editor for MyTree, click on the Construction Script tab.<\/li>
- Right-click in the empty window and type treetype. There is a Get number of entries in TreeType node:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/8a5f09a0-43b0-4d0e-852f-f28683ca8a5c.png\")
<\/figure>\n\n\n\n- Where and then connect its Return value output pin to the Max property of a new Random Integer node:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/aa62d8f0-eac4-4978-903c-33be135516cc.png\")
<\/figure>\n\n\n\n- Connect the Return Value output of the random integer to a ToByte (Integer) node:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"https:\/\/learning.oreilly.com\/library\/view\/unreal-engine-4x\/9781789809503\/assets\/e638984a-344d-4bcb-9d28-dc2bbdcfe361.png\")
<\/figure>\n\n\n\n- In the Variables section of the My Blueprint panel, click on the + button. From there, go to the Details tab and set the Variable Type to Tree Type. Afterward, set the Variable Name to RandomTree:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/43c68378-cfe8-4485-8e5f-1a654392ffb4.png\")
<\/figure>\n\n\n\n- Drag the RandomTree variable into the graph and select Set Random Tree when you see a small context menu appear.<\/li>
- Connect the Return Value output of the ToByte node to the input of the SET Type node. You’ll see an extra conversion node automatically appear.<\/li>
- Lastly, connect the execution pin of Construction Script to the SET Type node’s execution pin. Your Blueprint should look as follows:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/17bd491f-612b-4926-9485-76609cd128da.png\")
<\/figure>\n\n\n\n- To verify that the blueprint is correctly functioning and randomly assigning a type to our tree, we are going to add some nodes to the Event Graph.<\/li>
- Place a Print String node after the Event BeginPlay event node:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/155d1518-6a95-478b-89db-c434fbb4a3ea.png\")
<\/figure>\n\n\n\n- Place a Format Text node and connect its output to the input of the Print String node. A conversion node will be added for you:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/825ac029-d5de-496c-87fe-2f17a6ebcd72.png\")
<\/figure>\n\n\n\n- Inside the Format Text node, add My Type is {0}! to the Format text box:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/d1b858b3-6f18-4cba-a7c8-8d54f5137af8.png\")
<\/figure>\n\n\n\nYou should see that it adds a new parameter, 0, which we can now set.<\/p>\n\n\n\n
- Drag the RandomTree variable from the Variables section of the My Blueprint window into the graph and select Get from the menu:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/76fab5b0-2f7d-4c0e-a8d4-0ed39f776c22.png\")
<\/figure>\n\n\n\n- Add an Enum to Name node to the Type output pin:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/d92b7665-d8ed-4b79-b03a-ad3b56eb5f9f.png\")
<\/figure>\n\n\n\n- The Format Text node will not use a Name, so we will need to convert it into Text. Add a ToText (name) node to the Enum to Name output pin.<\/li>
- Connect the Return Value output of the ToText (name) node to the 0 input pin on the Format Text node. Your Event Graph should now look as follows:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"http:\/\/blog.coolcoding.cn\/wp-content\/uploads\/2021\/01\/f79e30f9-f9b9-46cf-8784-a4a7e93d8c40.png\")
<\/figure>\n\n\n\nThe completed Blueprint graph<\/p>\n\n\n\n
- Compile your Blueprint and then return to the Unreal Editor.<\/li>
- Drag a few copies of your Blueprint into the level and hit Play. You should see a number of trees printing information regarding their type, verifying that types are being randomly assigned by the Blueprint code that we created:<\/li><\/ol>\n\n\n\n
![\"\"\/](\"https:\/\/learning.oreilly.com\/library\/view\/unreal-engine-4x\/9781789809503\/assets\/b1534f7b-f726-4577-92d5-380d72ddacf2.png\")
<\/figure>\n\n\n\nHow it works…<\/h1>\n\n\n\n
As usual, we use StaticMeshActor as the base class for our Actor so that we can easily give it a visual representation in the level.<\/p>\n\n\n\n
Enumerated types are exposed to the reflection system using the UENUM macro.<\/p>\n\n\n\n
We mark the enum as Blueprint-available using the BlueprintType specifier.<\/p>\n\n\n\n
The enum declaration is just the same as we would use in any other context.<\/p>\n\n\n\n
Our Tree requires a TreeType. Because tree has tree-type<\/em> is the relationship we want to embody, we include an instance of TreeType in our Tree class.<\/p>\n\n\n\n
As usual, we need to use UPROPERTY() to make the member variable accessible to the reflection system.<\/p>\n\n\n\n
We use the BlueprintReadWrite specifier to mark the property as having both get and set support within Blueprint.<\/p>\n\n\n\n
Enumerated types require being wrapped in the TEnumAsByte template when used in UPROPERTY, so we declare an instance of TEnumAsByte<TreeType> as the Tree’s Type variable.<\/p>\n\n\n\n
The constructor changes for Tree are simply the standard load and initialize our static mesh component preamble that’s used in other recipes.<\/p>\n\n\n\n
We create a Blueprint that inherits from our Tree class so that we can demonstrate the Blueprint-accessibility of the TreeType enum.<\/p>\n\n\n\n
To have the Blueprint assign a type to the tree at random when we create an instance, we need to use the Construction Script Blueprint.<\/p>\n\n\n\n
Within the Construction Script, we calculate the number of entries in the TreeType enum.<\/p>\n\n\n\n
We generate a random number and use that as an index in the TreeType enum type to retrieve a value to store as our Type.<\/p>\n\n\n\n
The Random number node, however, returns integers. Enumerated types are treated as bytes in Blueprint, so we need to use a ToByte node, which can then be implicitly converted by Blueprint into an enum value.<\/p>\n\n\n\n
Now that we have Construction Script assigning a type to our tree instances as they are created, we need to display the tree’s type at runtime.<\/p>\n\n\n\n
We do so with the graph attached to the BeginPlay event within the Event Graph tab.<\/p>\n\n\n\n
To display text on screen, we use a Print String node.<\/p>\n\n\n\n
To perform string substitution and print our type out as a human-readable string, we use the Format Text node.<\/p>\n\n\n\n
The Format Text node takes terms enclosed in curly braces and allows you to substitute other values for those terms by returning the final string.<\/p>\n\n\n\n
To substitute our Type into the Format Text node, we need to convert our variable stores from the enum value into the actual name of the value.<\/p>\n\n\n\n
We can do so by accessing our Type variable and then using the Enum to Name node.<\/p>\n\n\n\n
Names, or FNames in native code, are a type of variable that can be converted into strings by Blueprint so that we can connect our Name to the input on the Format Text node.<\/p>\n\n\n\n
When we hit Play, the graph executes, retrieving the type of tree instances that have been placed in the level and printing the names to the screen.<\/p>\n","protected":false},"excerpt":{"rendered":"
Enums are commonly used in C++ as flags or inputs to sw […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27,1],"tags":[26],"_links":{"self":[{"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/posts\/3033"}],"collection":[{"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3033"}],"version-history":[{"count":3,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/posts\/3033\/revisions"}],"predecessor-version":[{"id":3352,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=\/wp\/v2\/posts\/3033\/revisions\/3352"}],"wp:attachment":[{"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3033"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3033"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.coolcoding.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3033"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
- Add an Enum to Name node to the Type output pin:<\/li><\/ol>\n\n\n\n
- Drag the RandomTree variable from the Variables section of the My Blueprint window into the graph and select Get from the menu:<\/li><\/ol>\n\n\n\n
- Inside the Format Text node, add My Type is {0}! to the Format text box:<\/li><\/ol>\n\n\n\n
- Place a Format Text node and connect its output to the input of the Print String node. A conversion node will be added for you:<\/li><\/ol>\n\n\n\n
- In the Variables section of the My Blueprint panel, click on the + button. From there, go to the Details tab and set the Variable Type to Tree Type. Afterward, set the Variable Name to RandomTree:<\/li><\/ol>\n\n\n\n
- Connect the Return Value output of the random integer to a ToByte (Integer) node:<\/li><\/ol>\n\n\n\n
- Where and then connect its Return value output pin to the Max property of a new Random Integer node:<\/li><\/ol>\n\n\n\n
- Add the following to the Tree constructor:<\/li><\/ol>\n\n\n\n
- Add the following to the Tree class:<\/li><\/ol>\n\n\n\n