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Or an alternative using events which gives us a historical log. We can combine it with Lauri Peltonen's example to make it so a document can only be set once. contract Timestamping { event logTime …

Your function is not a view function because it modifies and thus will be a transaction so it will not return a value , simply the tx receipt. The value can be returned to another function however, j …

Cryptozombies is cool indeed, also check out https://ethernaut.zeppelin.solutions/

I find the answer above confusing. It really boils down to this: Pure does (can) not access state only memory/stack View can access state but not make changes to it, just query (+ ETL). No state c …

In Solidity you can return values from functions to the user if these functions are declared view(/constant). When they are not declared as view you can still get a return value by using .call() this …

Send tx to create a new account, a contract account this is stored in the world state (which is a mapping of the accounts and account state) . This creates a contract storage, our smart contract's by …

Here's an example for upgradeable libraries. https://github.com/kyriediculous/knuckles/tree/master/contracts/contracts I'm currently working on cutting it down. There's a central registry to keep …

tl;dr the upgradeable part is the library which only contains logic, not storage. Only editing You can't do that since the interface in which you define your struct is linked to the storage contract …

You can trust the logs because they are stored in their respective block. If a log gets changed it would change the blockhash, receiptRoot, etc , same as with transactions. The merkle tree would not b …