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I keep on wanting to exercise a choice from another choice (for the same template). Is there a way to do this without knowing the contract id? i.e. I can't call exercise ??? MyChoice from the body of another choice, without knowing ???. Or am I trying to do something fundamentally wrong? Ideally something like exercise this.id MyChoice

Luciano
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2 Answers2

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There is an implicit variable self which is the contract ID of this given to every choice. So for example,

    nonconsuming choice NoConsume : Int
      controller p
      do return 41

    postconsuming choice PostConsume : Int
      controller p
      do (+2) <$> exercise self NoConsume -- Yes, fetching self in a postconsuming choice is ok.
Shayne Fletcher
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From an internal DA conversation:

moritz.kiefer 9 days ago exercise self MyChoice works iirc?

andrae.muys 9 days ago self was introduced for precisely this purpose. Be aware that the contract will be archived before your choice exercises in consuming choices. You need to use a post-consuming or non-consuming choice to avoid this.

Luciano 9 days ago Is postconsuming documented? I don't recall seeing it.

moritz.kiefer 9 days ago https://docs.daml.com/concepts/glossary.html#postconsuming-choice there is also a blogpost somewhere iirc

moritz.kiefer 9 days ago Found it https://blog.daml.com/daml-driven/daml-choice-annotations blog.daml.comblog.daml.com DAML choice annotations This post reviews the consuming concept and explains the meaning of the newly added preconsuming and postconsuming keywords.

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Luciano
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