Compose or use variable?

[Meneghino]

I am relatively new to Flow, can anyone clarify when one should use variables or when instead one should use Compose?
I am paricularly confused about Compose, not sure what it is and how it is different from a variable.

Many thanks!

PS I think @v-micsh-msft, @MikeInCairns or @ArtSys may be interested

[v-micsh-msft]

Hi @Meneghino,

It is recommended to take a look at the Flow blog:

Build more advanced flows than ever

Which explains how the compose is supposed to use:

"

If you have a single value that you want to re-use many different times throughout your flow (for example, a single message that you want to reuse in several emails you send out), you can now compose a string variable:

"

Basically a Compose Variable is only available to use as a container, Variables action has its corresponding action to update itself.

Regards,

Michael

[Meneghino]

Thanks @v-micsh-msft

I am still however a bit confused.  There is no Compose action in here:

https://docs.microsoft.com/en-us/azure/logic-apps/logic-apps-workflow-definition-language

Is there any documentation on Compose?

Does compose only contain a string or can it contain other types?

Also, it seems that Compose is almost like Collect() in PowerApps, in that it collects additional strings, as in the example in this blog post:

https://flow.microsoft.com/en-us/blog/email-digest-date-manipulations/

Is this so?

[v-micsh-msft · Accepted solution]

Hi @Meneghino,

Compose should be able to handle any kind of data Input.

Besides, I don't think Compose is similar to Collect() function.

I will try to explain from my own understanding.

Compare the whole Flow to math equation, then Compose Action should be considered as operators like +, -, *, /,

I think you have noticed that under Compose action in running details, there is only Outputs available,

Through the Compose Action, we could only get the result from the value input, but we can't change the Input, which means there is no way to modify the original input of the same compose,

For Variables, it should be the X parameter in the equation, which we could substitute with values,

Under the the running details, you should also noticed that it only contains Inputs, and it has the corresponding action to "Update" the X (original input) value.

Regards,

Michael

[Meneghino · Accepted solution]

Hi @v-micsh-msft

Thank you for following up.  In any case I have now found this documentation:

https://docs.microsoft.com/en-us/azure/logic-apps/logic-apps-workflow-actions-triggers#compose-actio...

It is not too clear, but also gives some indications.