onFieldAccess

OnFieldAccess.cyan

package metaobjectTest


@doc{*
    Annotations of this metaobject are attached to a field. 
    The attached DSL code is made in Myan, which supports interpreted Cyan
    within parameterless methods declared with 'func': 
    
        func afterResTypes_codeToAdd {    
            // interpreted Cyan code
        }
    
    According to the method name, the Cyan code is interpreted in phase
    afterResTypes or semAn. Methods of interfaces
        IAction_semAn
        IActionNewPrototypes_semAn
        IAction_afterResTypes
        IActionNewPrototypes_afterResTypes
        IParseWithCyanCompiler_parsing 
        ICommunicateInPrototype_afterResTypes_semAn_afterSemAn    
        IActionFieldAccess_semAn
        
    can be implemented. To better understand this, see the documentation 
    for action_afterResTypes_semAn.
*}
object OnFieldAccess

    func run {
        alwaysZero = 10;
        var value = alwaysZero;
        assert value == 0;
        assert howManyTimesCounterWasSet == 0;
        counter = 1;
        assert howManyTimesCounterWasSet == 1;
    }
    

    /* Each time the variable is set, field
       howManyTimesCounterWasSet is  incremented by 1. 
    */    
    @onFieldAccess{*
        func semAn_replaceSetField {
            var String name = fieldToSet asString;
            var String value = rightHandSideAssignment asString;
            return name ++ " = " ++ value ++ """;   ++howManyTimesCounterWasSet;""";
        }
    *}
    
    
    var Int counter = 0;
    var Int howManyTimesCounterWasSet = 0;

    /* Even if this field is set to another value, 
       its value will always be 0
    */    
    @onFieldAccess{*
        func semAn_replaceGetField {
            return "0";
        }
    *}
    var Int alwaysZero = 9;


end