MessagePlaceholder class final

Prompt template that assumes the variable is a ChatMessage (ChatMessageType.messagePlaceholder).

This is useful when you want to use a single ChatMessage in the prompt. For example, when you decide the type of message at runtime (e.g. HumanChatMessage or FunctionChatMessage).

If you need to add multiple messages, use MessagesPlaceholder.

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'),
]);
Inheritance
Annotations
  • @immutable

Constructors

MessagePlaceholder({required String variableName})
Prompt template that assumes the variable is a ChatMessage (ChatMessageType.messagePlaceholder).
const

Properties

defaultOptions → BaseLangChainOptions
The default options to use when invoking the Runnable.
finalinherited
hashCode → int
The hash code for this object.
no setterinherited
inputVariables → Set<String>
Input variables of all the messages in the prompt template.
no setteroverride
partialVariables → PartialValues?
Partial variables.
no setteroverride
prompt → BasePromptTemplate
The prompt template for the message.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
variableName → String
The name of the placeholder variable.
final

Methods

batch(List<InputValues> inputs, {List<BaseLangChainOptions>? options}) → Future<List<List<ChatMessage>>>
Batches the invocation of the Runnable on the given inputs.
inherited
bind(BaseLangChainOptions options) → RunnableBinding<InputValues, BaseLangChainOptions, List<ChatMessage>>
Binds the Runnable to the given options.
inherited
close() → void
Cleans up any resources associated with it the Runnable.
inherited
copyWith({BasePromptTemplate? prompt, String? variableName}) → ChatMessagePromptTemplate
Return a new ChatMessagePromptTemplate instance with the given values.
override
formatMessages([Map<String, dynamic> values = const {}]) → List<ChatMessage>
Format the prompt with the inputs returning a list of messages.
override
getCompatibleOptions(RunnableOptions? options) → BaseLangChainOptions?
Returns the given options if they are compatible with the Runnable, otherwise returns null.
inherited
invoke(InputValues input, {BaseLangChainOptions? options}) → Future<List<ChatMessage>>
Format the prompt with the inputs returning a list of messages.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
pipe<NewRunOutput extends Object?, NewCallOptions extends RunnableOptions>(Runnable<List<ChatMessage>, NewCallOptions, NewRunOutput> next) → RunnableSequence<InputValues, NewRunOutput>
Pipes the output of this Runnable into another Runnable using a RunnableSequence.
inherited
stream(InputValues input, {BaseLangChainOptions? options}) → Stream<List<ChatMessage>>
Streams the output of invoking the Runnable on the given input.
inherited
streamFromInputStream(Stream<InputValues> inputStream, {BaseLangChainOptions? options}) → Stream<List<ChatMessage>>
Streams the output of invoking the Runnable on the given inputStream.
inherited
toString() → String
A string representation of this object.
override
withFallbacks(List<Runnable<InputValues, RunnableOptions, List<ChatMessage>>> fallbacks) → RunnableWithFallback<InputValues, List<ChatMessage>>
Adds fallback runnables to be invoked if the primary runnable fails.
inherited
withRetry({int maxRetries = 3, FutureOr<bool> retryIf(Object e)?, List<Duration?>? delayDurations, bool addJitter = false}) → RunnableRetry<InputValues, List<ChatMessage>>
Adds retry logic to an existing runnable.
inherited

Operators

operator ==(covariant ChatMessagePromptTemplate other) → bool
The equality operator.
inherited