Nested Blocks: Templating Errors in CURL URLs with Variables | Dust Community

Nested Blocks: Templating Errors in CURL URLs with Variables

Hey Dust community! 👋 Found something interesting about nested blocks! When trying to use variables in CURL URLs within WHILE or MAP/REDUCE structures, we get a templating error. For example, in this sequence:

CODE_nested (sets some variables)
CURL_nested (tries to use those variables in URL)

We get: "Templating error: Variable not found in context while rendering 'url'" 😅 Anyone else encountered this? Any workarounds you've found? Thanks! 🙏

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4 comments

David Ebbo
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Hi Zoé. I think what's happening is that your CODE_nested block actually returns an array of all the values so far. So in the URL, you could write something like {{CODE_nested[0].yourvar}} . But this does seem quite quirky, so I'm also curious how this would be used in practice. I assume that your intent is to use whatever the code block returned in the same iteration of the while?
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Zoé Marquis
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Hello David! Thank you for the helpful insight about array indexing. You're absolutely right about the use case. Here's what I'm trying to achieve: I need to call 20+ API endpoints with different IDs. I was exploring two approaches:
WHILE loop to process each ID sequentially
MAP/REDUCE to handle a list of IDs in parallel
The main challenge I encountered was passing the current item's ID into the CURL URL within these loop structures.
Zoé Marquis
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Here's the working MAP/REDUCE structure I used: 1. CODE_PREPARE_ARRAY - Flattens nested data into array 2. MAP_PROCESS from that array 3. CODE_CURRENT_ITEM - Uses env.map.iteration to extract current item data 4. CURL_API_CALL - Uses {{CODE_CURRENT_ITEM.variable}} syntax directly 5. REDUCE_PROCESS collects results The intermediate CODE block with env.map.iteration works! You can access variables directly without [0] indexing.
David Ebbo
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Nice job in finding something that works! I guess MAP/REDUCE behaves differently from WHILE. For what it's worth, here is a tricky way to get the current item in the WHILE case, by setting the URL as follows: {% set last_element = CODE_NESTED | last %}somewhere.com?q={{last_element.variable}} So basically telling it to use the last element of the array, which is the current one. But yeah, that's quite dirty!
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