Dynamic size about arduinojson

[bblanchon]

That is a very curious feature request 😲

I think that the idea of a DynamicJsonObject that you create by merging JsonObjects is not handy.

In the other hand, I can try to draft a DynamicJsonObject that would automatically grow as you add data.
That would give you:

DynamicJsonObject dynamicObject;
dynamicObject["key1"] = 1;
dynamicObject["key2"] = 2;
dynamicObject["key3"] = 3;

It would implicitly call malloc(), realloc() and free(), breaking the idea of a "malloc-free" library; but in the other hand, it could be useful for some specific usages.

What do you think?

[leventesen]

Static allocation has more advantages in embedded systems but sometimes dynamic allocation can be necessary. Think about a configuration service object that keeps the config keys of the modules in the system and saves them into eeprom. In this example, configuration service object can not know the count of the keys. Modules define their config-sets as JsonObject and configuration service object merges them into DynamicJsonObject.

I think, both static & dynamic allocated Json library will be perfect. If you decide to implement this, we can talk more about the api and usage scenarios before coding.

[shreyasbharath]

I agree this would be a very useful addition for embedded systems that do use dynamic memory.

[bblanchon]

I like the idea of a library that provide both static and dynamic allocation.
I also like the idea of adding the word Dynamicto the names because the user is aware that he may be doing something dangerous.

I'll try to free some time on the week-end to write a draft version.
I'll keep you informed with the progress.

[bblanchon]

Done!

In version 4.1, you can use DynamicJsonBuffer in place of StaticJsonBuffer<N> to switch to a dynamic memory allocation.