Storing State in a Smart Contract
Storing State in a Smart Contract
Smart contracts give us the opportunity to store data in a stateful way, and where we can add and delete data within the smart contract, and then view a current state. So let’s do a simple contact of adding cities to a string array. Overall it will cost us some gas to add and delete strings, but not to view the state. The contract we will use is:
This has an add() method to add a new string to myArray, and a show() which will show the contents of myArray. The view element added to show() makes sure it is just a read function (and that we do not write to the function). We can then compile it in remix:
Now we can deploy:
This creates a new contact [here]:
If we look at the contract we get:
Next we can Verify the contract:
Note that the compiler we used is 0.4.24. We then add our code, and then the contact is validated:
It is now complete [here]:
This will cost us some gas as we change the state of the smart contact:
Once it has been mined, the smart contract will be updated:
We can then use the View() method to see the string:
Now we add “Glasgow”:
And once it has been mined, we can go back and show the new state:
Just magic! I love smart contracts!!!!
Go on, try my smart contract:
https://ropsten.etherscan.io/address/0xc79961ad2fdf3fcb4a57ebeaab78a1e3f8bf373c
And here’s the full example: