Hi, need help
Is there a way to create unique random number between range in solidity?

The best way to do this is using chainlink oracles, or even better generating the random number off-chain

Solidity doesn't have an inbuilt random number generator like other languages

I am using chainlink, but it won't me random number in range everytime

currently I'm generating a index using chainlink and using that number to select a value from array, and then pop that number from the array.
But this method is quite high on gas, is there any other way to this?

Not really, randomness doesnt exist in Math

You could do some random calculations like timestamp/blockNumber/walletNounce or whatever

If you only want to fish out an address of an array once an hour or so

But as soon as you allow transactions from users this is not safe

yeah exactly

Why dont you do it offchain

I need to pas it as tokenId to in ERC721 contract, passing token Id to an NFT contract is not the best practice

Apply bounds to your received random num

Already did, that's how i'm generating index between array length

Then what's the issue?

this method is very expensive on gas

It works fine, but very expensive

Huh how is that expensive? All you're doing is applying a mod (possibly an addition too).

i have to call it number of times

example if I want to mint 5 NFT, I need generate random index 5 times

Well, do repeated hashing and generate any number of random words you want. I still don't see the expensive part

you can call chainlink asking multiple random numbers in tx

then apply the modulo and done

https://twitter.com/devanoneth/status/1616253670860984321?t=3AmZ44bgUiC1lBWTtD_0yg&s=35