Solidity – How to Call Private/Internal Function from External Function in Solidity

accessdesign-patternssolidityvisibility

what the purpose of that way to restrict access to function call?

    function updateQuorumNumerator(uint256 newQuorumNumerator) external virtual onlyGovernance {
        _updateQuorumNumerator(newQuorumNumerator);
    }

    function _updateQuorumNumerator(uint256 newQuorumNumerator) internal virtual {
        require(
            newQuorumNumerator <= quorumDenominator(),
            "GovernorVotesQuorumFraction: quorumNumerator over quorumDenominator"
        );

        uint256 oldQuorumNumerator = _quorumNumerator;
        _quorumNumerator = newQuorumNumerator;

        emit QuorumNumeratorUpdated(oldQuorumNumerator, newQuorumNumerator);
    }

Why can't we just make _updateQuorumNumerator external and add modifier onlyGovernance to it?

Best Answer

One possible reason is for the sake of inheritance. If you wanted to use the logic within _updateQuorumNumerator without the onlyGovernance modifier in a child smart contract, you would want the external and internal logic to be separated.
It can simply be better to separate the two if you're going to allow the contract to be inherited from. By separating the two functionalities (external access and internal logic), you are maximizing code reusability.

Related Solutions

Solidity Mapping – Can Mapping Be Called as Arguments of Function?

The second error you get tells you that external functions cannot have internal types as arguments (i.e. structs and mappings). You can solve that one by specifying internal or private for your function.

For the first error, im not sure if it is a bug or not, but you cannot pass mappings as arguments. What you could do is wrap them in a struct and pass the struct as a parameter.

One final notice is that if you declare your mapping as a state variable then you have access to it directly in your function. So in you example table could just be a state variable...especially since you only use it for storage purposes.

[Ethereum] the difference between an internal/external and public/private function in solidity

The paragraph specifically mentions that only function types are by default internal, and contract functions are by default public, even though I agree the wording is a little bit confusing. It says nowhere that they are at the same time both public and internal.

I think that there is some confusion to what a function type is. The same way you specify the type for a 256 int variable with the keyword uint256, you can also specify the type of a variable that will hold a function. The only difference is that this type declaration is a little more complex since functions are more complex and it looks like this:

function (param types) {internal|external} [pure|constant|view|payable] [returns (return types)] varName;

You can then assign to the variable varName a function that has the same type that you defined. This is only possible inside another function.

As a very simple example:

contract Example{
    function(uint256) returns (uint256) varName;

    function simpleFunction(uint256 parameter) returns (uint256){
        return parameter;
    }

    function test(){
        varName = simpleFunction;
    }
}

Where varName is the variable of function type, while simpleFunction and test are normal contract functions

Just so you have a simple definition for all those access classifiers:

public - all can access
external - Cannot be accessed internally, only externally
internal - only this contract and contracts deriving from it can access
private - can be accessed only from this contract

As you can notice private is a subset of internal and external is a subset of public.

Best Answer

Related Solutions

Solidity Mapping – Can Mapping Be Called as Arguments of Function?

[Ethereum] the difference between an internal/external and public/private function in solidity

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