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Types conversations

One of the most important topics in context of tgbotapi is types conversations. This library is very strong-typed and a lot of things are based on types hierarchy. Lets look into the hierarchy of classes for the Message in 0.35.8: Message Diagram.png

As you may see, it is a little bit complex and require several tools for types conversation.


as conversations will return new type in case if it is possible. For example, when you got Message, you may use asContentMessage conversation to get message with content:

val message: Message;
println(message.asContentMessage() ?.content)

This code will print null in case when message is not ContentMessage, and content when is.


require works like as, but instead of returning nullable type, it will always return object with required type OR throw ClassCastException:

val message: Message;

This code will throw exception when message is not ContentMessage and print content when is.


when extensions will call passed block when type is correct. For example:

val message: Message;
message.whenContentMessage {

Code placed above will print content when message is ContentMessage and do nothing when not