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design_pattern_desicions.md

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Design Patterns Implemented

Access Restriction Pattern

OMarket and Store contracts have restictions on some methods respectively. Both contracts have Ownable pattern that some methods such as adding admins or creating new products are allowed by only the owner of the contract. This Ownership also can be transfarrable by the owner of the contract. This transfership is used in Store contract.

Also OMarket has additional restrictions that only Admins or Store Owners can take some actions.

For ownership it is used custom solutions couple with Open-Zeppelin https://docs.openzeppelin.org/v2.3.0/access-control#ownership-and-ownable Ownable contract.

Can be found more information about this pattern at; https://github.com/fravoll/solidity-patterns/blob/master/docs/access_restriction.md

Guard Check

Ensure that the behavior of a smart contract and its input parameters are as expected.

Both OMarket and Store contracts are checking input parameters as expected. Some examples are;

  • OMarket

    uint nextStoreId = storeIdGenerators[msg.sender]+1;
if (nextStoreId == STORE_CAP+1) {
  revert('Capped store count for this store owner');
}

  • Store

      require(balance!=0, 'Account balance is 0');

Can be found more information about this pattern at; https://github.com/fravoll/solidity-patterns/blob/master/docs/guard_check.md

Circuit Breaker / Emergency Stop Pattern

Emergency stop pattern is implemented by using Open-Zeppelin Pausable https://docs.openzeppelin.org/v2.3.0/api/lifecycle#pausable contract on OMarket. Contract module which allows children to implement an emergency stop mechanism that can be triggered by an authorized account.

Owner account (Authorized accounts) can pause or unpause the contract. Also owner can add additional pauser roled accounts. Following methods can be done by only the contract is not paused by using the modifier whenNotPaused;

  • addAdmin
  • addStoreOwner
  • toggleStoreOwnerStatus
  • addNewStore

Can be found more information about this pattern at; https://github.com/fravoll/solidity-patterns/blob/master/docs/emergency_stop.md