Recomendation!

[idimon4uk]

https://github.com/robertsimoes/Solidity-Contract-Patterns/blob/master/IndexedStructMap/IndexedStructMap.sol
If I was u, I would develop update and add as one function, for example using

mapping(uint => address)

and have uint size; and write 2 maps and size in 1 struct;
something like this:

struct eDataStruct {
mapping(address => Entity) entityStructs;
mapping(uint=>address) entityList;
uint size;
}
struct Entity { 
    uint eData; 
    bool exists; 
  } 

[idimon4uk]

using arrays in smart-contracts it's bad idea )

[aquaflamingo]

Thanks for the recco @idimon4uk, Interesting!!

Could you elaborate on why you think array's aren't the best idea?

[idimon4uk]

it's my own opinion, I had some experience with arrays. it's too easy to update some data using map , and have some problem using arrays, for example 'out of gas'. it's depended from task