Ethereum Asked on December 4, 2021
I am using the function mentioned below to delete a user (i added delete entityList[rowToDelete] to the function )My main issue is that the function deletes the user but somehow I lose the data in string items[]
from other users
struct EntityStruct {
uint entityData;
// other stuff
string items[]; <--------- I lose the data in here/Cannot fetch the data from the array anymore
}
mapping(address => EntityStruct) public entityStructs;
address[] public entityList;
function deleteEntity(address entityAddress) public returns(bool success) {
if(!isEntity(entityAddress)) throw;
uint rowToDelete = entityStructs[entityAddress].listPointer;
address keyToMove = entityList[entityList.length-1];
entityList[rowToDelete] = keyToMove;
entityStructs[keyToMove].listPointer = rowToDelete;
entityList[rowToDelete]
entityList.length--;
return true;
}
You've got an array of strings inside the entity. This is valid but not necessarily what you want.
Each entity contains a list. When you delete an entity, you delete the list that was inside it.
If that's surprising or unintended, possibly what you really want is two entities. There may be a relationship between the entities that you want to enforce at the contract level. In that case, the general idea is to hold a list of related keys in this entity, and hold the records that are supposed to survive in a separate structure.
More on that pattern over here: https://medium.com/@robhitchens/enforcing-referential-integrity-in-ethereum-smart-contracts-a9ab1427ff42
Hope it helps.
Answered by Rob Hitchens on December 4, 2021
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