# {String: String} broken in Flow Playground

**URL:** <https://forum.flow.com/t/string-string-broken-in-flow-playground/1398>\
**Category:** Flow Playground\
**Created:** [March 11, 2021, 2:50am UTC](https://forum.flow.com/t/string-string-broken-in-flow-playground/1398 "2021-03-11T02:50:55Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![FranklinsHand](https://avatars.discourse-cdn.com/v4/letter/f/d2c977/32.png) [@FranklinsHand](https://forum.flow.com/u/FranklinsHand)\
**Post date:** [March 11, 2021, 2:50am UTC](https://forum.flow.com/t/string-string-broken-in-flow-playground/1398/1 "2021-03-11T02:50:55Z")

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Whenever I attempt to use the {String: String} input for transactions I get this error  
`Error: GraphQL error: failed to decode argument 0: failed to decode value: invalid JSON Cadence structure`  
I brought the code down to its simplest form

> transaction(metadata: {String: String}) {  
> prepare(acct: AuthAccount) {}  
> execute {  
> log(metadata)  
> }  
> }

And I use the simplest JSON Cadence object straight from the documentation  
`{"type": "Void"}`

But no matter what I do I still get the same error.  
I am trying to build a resource that utilizes JSON for it’s metadata, so any help here would be huge.

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**Author:** ![jnuno98](https://avatars.discourse-cdn.com/v4/letter/j/e68b1a/32.png) [@jnuno98](https://forum.flow.com/u/jnuno98)\
**Post date:** [April 10, 2021, 4:35pm UTC](https://forum.flow.com/t/string-string-broken-in-flow-playground/1398/2 "2021-04-10T16:35:38Z")

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i have the exact same problem

did you manage to find a solution to this?

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<div class="post-metadata">

**Author:** ![FranklinsHand](https://avatars.discourse-cdn.com/v4/letter/f/d2c977/32.png) [@FranklinsHand](https://forum.flow.com/u/FranklinsHand)\
**Post date:** [April 10, 2021, 5:26pm UTC](https://forum.flow.com/t/string-string-broken-in-flow-playground/1398/3 "2021-04-10T17:26:27Z")

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quite sadly, no. It seem that the playground itself does not support cadence objects. But I have no idea why.

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**Author:** ![bastian](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.flow.com/bastian/32/183_2.png) [@bastian](https://forum.flow.com/u/bastian)\
**Post date:** [April 16, 2021, 2:35pm UTC](https://forum.flow.com/t/string-string-broken-in-flow-playground/1398/4 "2021-04-16T14:35:38Z")

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Thank you for reporting this!

I’ve opened a bug report for it: [Complex arguments are not working · Issue #141 · onflow/flow-playground · GitHub](https://github.com/onflow/flow-playground/issues/141)