If you've ever noticed Blueprint errors after a PIE session, you'll see that they includes links that send you directly to a particular Blueprint node. This is because Epic is making use of Tokenized Messages in the Message Log. This article will outline how to use the FTokenizedMessage struct with Message Logs. We recommend that you look over the use of Message Logs before proceeding to use Tokenized Messages.

Mental Preparation

Before we begin, it helps to be aware that the Logging and Message features should be treated as Editor-Only. Any snippets of code or functions called within tokens should be wrapped inside of our #if WITH_EDITOR or #if WITH_EDITORONLY_DATA directives. These prevent editor-only features from being included in packaged builds and throwing errors at package time. You'll also want to wrap header includes with the same directives.

FTokenizedMessage

A tokenized message needs to be created before we can add anything to it. We can do this by calling the Create static method on the FTokenizedMessage class.

#if WITH_EDITOR
#include "Logging/TokenizedMessage.h"
#include "Logging/MessageLog.h"
#endif

#if WITH_EDITOR
void AMyLoggingClass::LoggingClassMethod() 
{
    FMessageLog PIE("PIE")

    TSharedRef<FTokenizedMessage> ErrorMessageToken = FTokenizedMessage::Create(EMessageSeverity::Type::Error);
}

#endif

When we eventually add all of the tokens to our message and are ready to pass it to the message log, we do so like this:

PIE.AddMessage(ErrorMessageToken);

When we create the Tokenized Message, we need to select a severity for the message as you can see above. The options for severity are:

namespace EMessageSeverity
{
	enum Type : int
	{
		CriticalError UE_DEPRECATED(5.1, "CriticalError was removed because it can't trigger an assert at the callsite. Use 'checkf' instead.") = 0,
		Error = 1,
		PerformanceWarning = 2,
		Warning = 3,
		Info = 4,
	};
}

Note that CriticalError is deprecated as of 5.1.

So if we wanted to pass an empty tokenized message to the message log, the full function would look like this:

void AMyLoggingClass::LoggingClassMethod() 
{
    FMessageLog PIE("PIE")

    TSharedRef<FTokenizedMessage> ErrorMessageToken = FTokenizedMessage::Create(EMessageSeverity::Type::Error);
    PIE.AddMessage(ErrorMessageToken)
}

However, that's not much different from adding an FText message to the log. So let's look at what tokenized messages can offer — tokens.

Adding Your First Token

To add a token to a message, you can use the arrow operator on the FTokenizedMessage sharedref.

void AMyLoggingClass::LoggingClassMethod() 
{
    FMessageLog PIE("PIE")

    TSharedRef<FTokenizedMessage> ErrorMessageToken = FTokenizedMessage::Create(EMessageSeverity::Type::Error);
    ErrorMessageToken->AddText(FText::FromString("The text part of the message. "))
    
    PIE.AddMessage(ErrorMessageToken)
}

The AddText() method creates what's called an FTextToken, which is one of the 14 types of tokens as of Unreal Engine 5.5. The Text Token simply adds and displays text messages wherever they're added in the flow of the Tokenized Message.

If we wanted to add another token after that one, we would do so like this:

void AMyLoggingClass::LoggingClassMethod() 
{
    FMessageLog PIE("PIE")

    TSharedRef<FTokenizedMessage> ErrorMessageToken = FTokenizedMessage::Create(EMessageSeverity::Type::Error);
    ErrorMessageToken->AddText(FText::FromString("The text part of the message. "))
        ->AddText(FText::FromString("Here's some more text."))
    
    PIE.AddMessage(ErrorMessageToken)
}

Each token creation method returns the reference to the FTokenizedMessage that it's a part of. This allows us to chain token addition calls with ease.

Hopefully by now you can see the utility of tokenized messages, at least to a certain degree. Before we go further, here are all 14 token types.

namespace EMessageToken
{
	enum Type
	{
		Action,
		Actor,
		AssetName,
		AssetData,
		Documentation,
		Image,
		Object,
		Severity,
		Text,
		Tutorial,
		URL,
		EdGraph,
		DynamicText,
		Fix,
	};
}

Each token inherits from the IMessageToken abstract class. We'll go over each one in detail do you can see how they work.

Action Token

Actor Token

Asset Name Token

Asset Data Token

Documentation Token

Image Token

Object Token

Severity Token

Text Token

Tutorial Token

URL Token

EdGraph Token

Dynamic Text Token

Fix Token