avenant_specifique.sol

pragma solidity ^0.4.8;

/**
 * Interface shared by Proxy, ContractV1 and ContractV2.
 */
contract Interface {
    /** return uint, depend of the current version. */
    function doSomething() constant returns(uint);
}

/**
 * A contract with amendment.
 * The attr is initialized to 1000.
 * The method doSomething() return attr + version = 1001
 */
contract Contract is Interface {
    uint constant private version=1;
    uint public attr=1000;

/*
    Impossible to use modifier ! You must insert this kind of code in each method.
    modifier viaAmendment() {
        if ((address(amendment) != 0) && (msg.sender != address(amendment))) { 
            return ???
        }
        else
            _;
    }
*/    
    function doSomething() constant returns(uint) {
        if ((address(amendment) != 0) && (msg.sender != address(amendment))) { 
            return amendment.doSomething();
        }
        else
            return attr+version;
    }

    // -- Technical functions and attributs
    /** Amendment. */
    Interface public amendment;
    
    /** Set amendment. */
    function setAmendment(Interface _amendment) {
        amendment=_amendment;
    }
    
}

/** 
 * An amendment.
 */
contract Amendment is Interface {
    uint constant private version=2;
    uint newAttr=100;
    
    /**
     * The new version of the method doSomething.
     */
    function doSomething() constant returns(uint) {
        return origin.attr()+newAttr+version;
    }

    /**
     * This new method can't be called.
     */
    function doOtherThing() constant returns(uint) {
        return 42;
    }

    // -- Technical functions and attributs
    /** Origin contract. */
    Contract public origin;
    
    /**
     * New amendment linked with the original contract.
     */
    function Amendment(Contract _origin) {
        origin=_origin;
    }
}

// -------------
/** 
 * Unit test.
 * 
 * After created an instance, 
 * - call 'init()'
 * - call 'doSomething()' return 1001
 * - call 'changeToV2'
 * - call 'doSomething()' return 1102
 */
contract A_UnitTest {
    Contract private aContract;

    function init() {
        aContract=new Contract();
    }
    function doSomething() constant returns(uint) {
        return aContract.doSomething();
    }
    function doOtherThing() constant returns(uint) {
        throw; // Not implemented
    }
    
    /** Change to V2. */
    function changeToV2() {
        aContract.setAmendment(new Amendment(aContract));
    }
}