My smart-contract has a mapping for Token-ID’s and their Prices, declared as follows:
mapping (uint256 => uint256) public tokenIdAndItsPriceMapping; -I intend to have only 5,000 tokens in total, and I want to pre-set their prices during the Contract’s deployment, but do so in ranges. Here’s what I mean:
-Tokens 0 through 49 are going to be 0.1 ETH -Tokens 50 through 99 are going to be 0.2 ETH -Tokens 100 through 149 are going to be 0.3 ETH
etc.
I can obviously do this in the Constructor using FOR loops, as follows:
// 0 -- 49 for(uint i = 0; i <= 49; i++) { tokenIdAndItsPriceDictionary[i] = 1000000000000000000 wei; // 0.1 ETH } // 50 -- 99 for(uint i = 50; i <= 99; i++) { tokenIdAndItsPriceDictionary[i] = 2000000000000000000 wei; // 0.2 ETH } // etc. But with there being 5,000 values to fill, that’s still going to require quite a lot of FOR loops - such that I might reach the Block’s Gas Limit during the contract’s deployment - causing it to fail. And if the project’s requirements were to change such that 10,000 Tokens will be needed instead of 5,000, what then?
Ordinarily - meaning in other languages, we can easily create a fixed-length Array and pre-populate it with default values - which would come in very handily for this. But it doesn't look like Solidity lets you do this.
Another approach would be to create a function that’ll return any particular Token’s price using it’s ID - and a big long IF statement:
function getTokenPrice(uint256 tokenID) returns (uint 256) { if(tokenID >= 0 && tokenID <= 49) { tokenIdAndItsPriceDictionary[tokenID] = 1000000000000000000 wei; // 0.1 ETH } else if(tokenID >= 50 && tokenID <= 99) { tokenIdAndItsPriceDictionary[tokenID] = 2000000000000000000 wei; // 0.2 ETH } else if(tokenID >= 100 && tokenID <= 149) { tokenIdAndItsPriceDictionary[tokenID] = 3000000000000000000 wei; // 0.3 ETH } // etc. return tokenIdAndItsPriceDictionary[tokenID] } This could work - but for only one Token at a time.
What if I wanted to have a function that returns ALL the prices of all the Tokens all at once, in one big Array? Like what if my front-end web3 App needed to get all those prices from the smart-contract as it loaded into the browser?
