{"id":455729,"date":"2025-04-12T03:00:13","date_gmt":"2025-04-12T03:00:13","guid":{"rendered":"http:\/\/savepearlharbor.com\/?p=455729"},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-29T21:00:00","slug":"","status":"publish","type":"post","link":"https:\/\/savepearlharbor.com\/?p=455729","title":{"rendered":"UENUM iteration in Unreal Engine<\/span>"},"content":{"rendered":"
<\/div>\n
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Preface<\/h3>\n

I needed to create a category panel for placeable items in the UI \u2014 like the ones you see in city-building games. As a legacy, I inherited a ready-made UENUM<\/code>, which may be modified in the future.<\/p>\n

Naturally, I didn\u2019t want to manually create and tweak every single widget \u2014 especially knowing that the list of categories might change later. I wanted something simple and reusable: just run a For each loop<\/code>, generate everything on the fly, and ideally make it work for any enum, not just this one.<\/p>\n

And there was<\/em> a way! When you define a UENUM<\/code>, Unreal automatically generates all the metadata and creates a corresponding UEnum<\/code> object, which is a UObject<\/code>. All you have to do is use that data properly.<\/p>\n\n

Creating uenum iterator<\/h3>\n

For convenience, we will use UBlueprintAsyncActionBase<\/code>, although it is not the only way.<\/p>\n

Let’s create an inheritor class UEnumIterateAction<\/code>.<\/p>\n

\n.h file<\/summary>\n
\n
#pragma once  #include \"CoreMinimal.h\" #include \"Kismet\/BlueprintAsyncActionBase.h\" #include \"EnumIterateAction.generated.h\"  DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnEnumIteration, const uint8, EnumValue);  \/**  *   *\/ UCLASS() class YOUR_MODULE_API UEnumIterateAction : public UBlueprintAsyncActionBase { GENERATED_BODY()  public:     \/** Our execution output at each iteration.*\/ UPROPERTY(BlueprintAssignable) FOnEnumIteration OnEnumIteration;      \/** The function itself, which we will call(almost).*\/ UFUNCTION(BlueprintCallable, BlueprintInternalUseOnly) static UEnumIterateAction* IterateByEnum(UEnum* Enum, const bool SkipMax = true);  protected: virtual void Activate() override;  private: TWeakObjectPtr EnumToIterate; uint8 bSkipMax : 1; }; <\/code><\/pre>\n<\/div>\n<\/details>\n
 What are we doing here?<\/strong><\/p>\n
I won\u2019t dive deep into UBlueprintAsyncActionBase<\/code> \u2014 this article isn\u2019t really about that. I\u2019ll just cover the relevant parts.<\/p>\n
First, we create the IterateByEnum<\/code> function, which acts as our constructor. The first argument is the UEnum<\/code> we want to iterate through. Since enums created in Blueprints automatically get a hidden MAX<\/code> value at the end, it\u2019s a good idea to optionally skip it \u2014 so we\u2019ll add a flag for that as the second argument.<\/p>\n
The OnEnumIteration<\/code> delegate will be triggered on each iteration. Think of it as the \u201casync\u201d execution pin. Just make sure to use a uint8<\/code> for the value, since that\u2019s how we\u2019ll represent enum entries and cast them back in Blueprints.<\/p>\n
Next, we override the Activate<\/code> function from the base class. That\u2019s where the actual logic goes \u2014 the body of our callable node.<\/p>\n
And because IterateByEnum<\/code> works like a constructor, we need to store the input arguments for use in Activate<\/code>. So, we\u2019ll add two member fields: EnumToIterate<\/code> and bSkipMax<\/code>.<\/p>\n
That\u2019s all for setup \u2014 let\u2019s move on to the implementation.<\/p>\n
Iterator implementation<\/h3>\n
\n.cpp file<\/summary>\n
\n
#include \"AsyncActions\/EnumIterateAction.h\"  UEnumIterateAction* UEnumIterateAction::IterateByEnum(UEnum* Enum, const bool SkipMax) { const auto Action = NewObject<UEnumIterateAction>(); if (!IsValid(Action)) return nullptr;  Action->EnumToIterate = Enum; Action->bSkipMax = SkipMax;  return Action; }  void UEnumIterateAction::Activate() { Super::Activate();  if (!EnumToIterate.IsValid()) return;  for (int32 Index = 0; Index < EnumToIterate->NumEnums(); ++Index) {         \/\/ Get the current enum value and check if it is maximal         const int64 EnumValue = EnumToIterate->GetValueByIndex(Index);         if (bSkipMax && EnumValue == EnumToIterate->GetMaxEnumValue()) continue;          \/\/ Convert the enum value to byte, for conversion into blueprints         const uint8 EnumValueAsByte = static_cast<uint8>(EnumValue);          OnEnumIteration.Broadcast(EnumValueAsByte); } } <\/code><\/pre>\n<\/div>\n<\/details>\n
 What\u2019s going on here?<\/strong><\/p>\n
The implementation of our IterateByEnum<\/code> function is pretty straightforward. As mentioned earlier, it basically works like a constructor, so we won\u2019t spend time on it here.<\/p>\n
Inside the Activate<\/code> function, we access the stored enum and loop through it using a standard for<\/code> loop \u2014 just like you would with an array.<\/p>\n
Unreal stores enum values as int64<\/code>, so that\u2019s the type we get when accessing them by index. But for our purposes, we need a Byte<\/code>, since that\u2019s the only type Blueprints can convert back into an enum value.<\/p>\n
It\u2019s also important to skip hidden enum entries \u2014 they\u2019re usually not meant to be shown anyway.<\/p>\n
We\u2019ve also added a flag to optionally skip the auto-generated MAX<\/code> entry, which often doesn\u2019t hold any meaningful value either. Since MAX<\/code> is also stored as an int64<\/code>, we compare the raw EnumValue<\/code> with the result of GetMaxEnumValue<\/code> before converting it to a Byte<\/code>.<\/p>\n\n
Result<\/h3>\n
\"Call<\/p>\n
Call of the iterator function<\/figcaption><\/div>\n<\/figure>\n
\"Output<\/p>\n
Output of enum values<\/figcaption><\/div>\n<\/figure>\n
\"Initial<\/p>\n
Initial enum values<\/figcaption><\/div>\n<\/figure>\n
As you can see, everything works great!<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n
<\/div>\n

 \u0441\u0441\u044b\u043b\u043a\u0430 \u043d\u0430 \u043e\u0440\u0438\u0433\u0438\u043d\u0430\u043b \u0441\u0442\u0430\u0442\u044c\u0438  https:\/\/habr.com\/ru\/articles\/900138\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
<\/div>\n
\n
\n
\n
\n
Preface<\/h3>\n
I needed to create a category panel for placeable items in the UI \u2014 like the ones you see in city-building games. As a legacy, I inherited a ready-made UENUM<\/code>, which may be modified in the future.<\/p>\n
Naturally, I didn\u2019t want to manually create and tweak every single widget \u2014 especially knowing that the list of categories might change later. I wanted something simple and reusable: just run a For each loop<\/code>, generate everything on the fly, and ideally make it work for any enum, not just this one.<\/p>\n
And there was<\/em> a way! When you define a UENUM<\/code>, Unreal automatically generates all the metadata and creates a corresponding UEnum<\/code> object, which is a UObject<\/code>. All you have to do is use that data properly.<\/p>\n\n
Creating uenum iterator<\/h3>\n
For convenience, we will use UBlueprintAsyncActionBase<\/code>, although it is not the only way.<\/p>\n
Let’s create an inheritor class UEnumIterateAction<\/code>.<\/p>\n
\n.h file<\/summary>\n
\n
#pragma once  #include \"CoreMinimal.h\" #include \"Kismet\/BlueprintAsyncActionBase.h\" #include \"EnumIterateAction.generated.h\"  DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnEnumIteration, const uint8, EnumValue);  \/**  *   *\/ UCLASS() class YOUR_MODULE_API UEnumIterateAction : public UBlueprintAsyncActionBase { GENERATED_BODY()  public:     \/** Our execution output at each iteration.*\/ UPROPERTY(BlueprintAssignable) FOnEnumIteration OnEnumIteration;      \/** The function itself, which we will call(almost).*\/ UFUNCTION(BlueprintCallable, BlueprintInternalUseOnly) static UEnumIterateAction* IterateByEnum(UEnum* Enum, const bool SkipMax = true);  protected: virtual void Activate() override;  private: TWeakObjectPtr EnumToIterate; uint8 bSkipMax : 1; }; <\/code><\/pre>\n<\/div>\n<\/details>\n
 What are we doing here?<\/strong><\/p>\n
I won\u2019t dive deep into UBlueprintAsyncActionBase<\/code> \u2014 this article isn\u2019t really about that. I\u2019ll just cover the relevant parts.<\/p>\n
First, we create the IterateByEnum<\/code> function, which acts as our constructor. The first argument is the UEnum<\/code> we want to iterate through. Since enums created in Blueprints automatically get a hidden MAX<\/code> value at the end, it\u2019s a good idea to optionally skip it \u2014 so we\u2019ll add a flag for that as the second argument.<\/p>\n
The OnEnumIteration<\/code> delegate will be triggered on each iteration. Think of it as the \u201casync\u201d execution pin. Just make sure to use a uint8<\/code> for the value, since that\u2019s how we\u2019ll represent enum entries and cast them back in Blueprints.<\/p>\n
Next, we override the Activate<\/code> function from the base class. That\u2019s where the actual logic goes \u2014 the body of our callable node.<\/p>\n
And because IterateByEnum<\/code> works like a constructor, we need to store the input arguments for use in Activate<\/code>. So, we\u2019ll add two member fields: EnumToIterate<\/code> and bSkipMax<\/code>.<\/p>\n
That\u2019s all for setup \u2014 let\u2019s move on to the implementation.<\/p>\n
Iterator implementation<\/h3>\n
\n.cpp file<\/summary>\n
\n
#include \"AsyncActions\/EnumIterateAction.h\"  UEnumIterateAction* UEnumIterateAction::IterateByEnum(UEnum* Enum, const bool SkipMax) { const auto Action = NewObject<UEnumIterateAction>(); if (!IsValid(Action)) return nullptr;  Action->EnumToIterate = Enum; Action->bSkipMax = SkipMax;  return Action; }  void UEnumIterateAction::Activate() { Super::Activate();  if (!EnumToIterate.IsValid()) return;  for (int32 Index = 0; Index < EnumToIterate->NumEnums(); ++Index) {         \/\/ Get the current enum value and check if it is maximal         const int64 EnumValue = EnumToIterate->GetValueByIndex(Index);         if (bSkipMax && EnumValue == EnumToIterate->GetMaxEnumValue()) continue;          \/\/ Convert the enum value to byte, for conversion into blueprints         const uint8 EnumValueAsByte = static_cast<uint8>(EnumValue);          OnEnumIteration.Broadcast(EnumValueAsByte); } } <\/code><\/pre>\n<\/div>\n<\/details>\n
 What\u2019s going on here?<\/strong><\/p>\n
The implementation of our IterateByEnum<\/code> function is pretty straightforward. As mentioned earlier, it basically works like a constructor, so we won\u2019t spend time on it here.<\/p>\n
Inside the Activate<\/code> function, we access the stored enum and loop through it using a standard for<\/code> loop \u2014 just like you would with an array.<\/p>\n
Unreal stores enum values as int64<\/code>, so that\u2019s the type we get when accessing them by index. But for our purposes, we need a Byte<\/code>, since that\u2019s the only type Blueprints can convert back into an enum value.<\/p>\n
It\u2019s also important to skip hidden enum entries \u2014 they\u2019re usually not meant to be shown anyway.<\/p>\n
We\u2019ve also added a flag to optionally skip the auto-generated MAX<\/code> entry, which often doesn\u2019t hold any meaningful value either. Since MAX<\/code> is also stored as an int64<\/code>, we compare the raw EnumValue<\/code> with the result of GetMaxEnumValue<\/code> before converting it to a Byte<\/code>.<\/p>\n\n
Result<\/h3>\n
\n
Call of the iterator function<\/figcaption><\/div>\n<\/figure>\n
\n
Output of enum values<\/figcaption><\/div>\n<\/figure>\n
\n
Initial enum values<\/figcaption><\/div>\n<\/figure>\n
As you can see, everything works great!<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n
<\/div>\n

 \u0441\u0441\u044b\u043b\u043a\u0430 \u043d\u0430 \u043e\u0440\u0438\u0433\u0438\u043d\u0430\u043b \u0441\u0442\u0430\u0442\u044c\u0438  https:\/\/habr.com\/ru\/articles\/900138\/<\/a>
<\/br><\/br><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-455729","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=\/wp\/v2\/posts\/455729","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=455729"}],"version-history":[{"count":0,"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=\/wp\/v2\/posts\/455729\/revisions"}],"wp:attachment":[{"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=455729"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=455729"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/savepearlharbor.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=455729"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}