How to pass struct mappings to solidity functions?

Question

I have two mappings (uint => customStruct) called listA and listB. I want to run both through a single function to perform operations on the contents.

How do I pass this type into a function so that I can call someFunction(listA) and someFunction(listB)?

I get errors like Type is required to live outside storage.

Ok, so I have found this which sounds related.. data-storage — slothbag, Feb 04 '16 at 10:20
Feel free to write your own answer (instead of a comment) and include details, not just a link. — eth, Feb 04 '16 at 11:04
Thanks, I haven't found a solution yet. The link was just a "might help" addition. — slothbag, Feb 04 '16 at 11:36
It's worth noting that you cannot iterate over a mapping nor can you check whether a key exists in a mapping. In solidity, mappings exist as if every key was present and had zero's as all of it's values. — Piper Merriam, Feb 07 '16 at 06:17

score 4 · Answer 1 · answered Feb 07 '16 at 06:17

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All storage variables declared in a contract are available within the scope of all of the functions of that contract. You do not need to pass them into your contracts functions to access them.

answered Feb 07 '16 at 06:17

Piper Merriam

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score 4 · Answer 2 · answered Feb 15 '16 at 11:41

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I got confirmation from Chriseth that this is probably a bug in Solidity that is not allowing a mapping to be sent as a parameter.

I worked around the problem by wrapping the parameter in a struct, and of course you need to use the storage keywork.

someFunction(myStruct storage myInstance){}

answered Feb 15 '16 at 11:41

slothbag

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I'm getting a similar error now. Is it possible this bug still exists? Is there a tracking issue in github somewhere? – carver Jun 08 '16 at 05:57

How to pass struct mappings to solidity functions?

2 Answers2

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