MessagesPlaceholder constructor

const MessagesPlaceholder({
  1. required String variableName,
})

Prompt template that assumes the variable is a list of ChatMessage (ChatMessageType.messagesPlaceholder).

This is useful for when you want to use a list of messages in the prompt. For example, after retrieving them from memory.

If you need to add a single message, use MessagePlaceholder.

Example:

ChatPromptTemplate.fromPromptMessages([
  ChatMessagePromptTemplate.system('You are a helpful AI assistant'),
  ChatMessagePromptTemplate.messagesPlaceholder('history'),
  ChatMessagePromptTemplate.messagePlaceholder('input'),
]);

Alternatively, you can use ChatPromptTemplate.fromTemplates to achieve the same result.

final promptTemplate = ChatPromptTemplate.fromTemplates([
  (ChatMessageType.system, 'You are a helpful AI assistant'),
  (ChatMessageType.messagesPlaceholder, 'history'),
  (ChatMessageType.messagePlaceholder, 'input'),
]);

Implementation

const MessagesPlaceholder({required this.variableName})
  : super(
      prompt: const PromptTemplate(inputVariables: {}, template: ''),
    );