# FAQ: Can we use nested dictionaries in Cadence?

**URL:** <https://forum.flow.com/t/faq-can-we-use-nested-dictionaries-in-cadence/949>\
**Category:** 🏄🏻‍♀️ Cadence\
**Created:** [February 16, 2021, 7:54pm UTC](https://forum.flow.com/t/faq-can-we-use-nested-dictionaries-in-cadence/949 "2021-02-16T19:54:08Z")\
**Posts on this page:** 1\
**Page:** 1

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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:** [February 16, 2021, 7:54pm UTC](https://forum.flow.com/t/faq-can-we-use-nested-dictionaries-in-cadence/949/1 "2021-02-16T19:54:08Z")

</div>

> I was trying to use something like this:
> 
> ```auto
> pub contract Test {
> pub let retired: {UInt32: {UInt32: Bool}}
> 
> init() {
> self.retired = {}
> }
> 
> pub fun retire(playerID: UInt32, series: UInt32) {
> self.retired[playerID][series] = true
> }
> }
> 
> ```
> 
> but I’m getting this error; “cannot index into value which have type {UInt32: Bool}?”.  
> Am I missing something?

Nested dictionaries are supported in Cadence.

The error message here points to the fact that the lookup of key `playerID` in dictionary `retired` might fail, i.e. there might be a case where there is no value for a given key. In that case, the lookup results in `nil`. Dictionary lookups in Cadence return an optional, the “not existing” case must be handled explicitly.

For this particular example, it is probably a good idea to create an empty nested dictionary when it does not exists:

```auto
pub fun retire(playerID: UInt32, series: UInt32) {
    let nested = self.retired[playerID] ?? {}
    nested[series] = true
    self.retired[playerID] = nested
}

```

Basically, first get the nested dictionary – if it does not exist, create an empty one.  
Second, set the value in the nested dictionary.  
Finally, insert the updated nested dictionary in the outer dictionary.