コードの恵み

■[.groovy] Named arguments

コンパイラさんに教えてもらった。

def aMethodHasNamedArguments(Map named=[:], Object... args) {
  println "named=$named, args=$args"
}

aMethodHasNamedArguments("A", key1:1, "B", key2:2, "C")
// named=[key1:1, key2:2], args=[A, B, C]

aMethodHasNamedArguments()
// named=[:], args=[]

Groovy 1.8.6 の AntlrParserPlugin より

        if (namedArguments) {
            if (!expressionList.isEmpty()) {
                // let's remove any non-MapEntryExpression instances
                // such as if the last expression is a ClosureExpression
                // so let's wrap the named method calls in a Map expression
                List<Expression> argumentList = new ArrayList<Expression>();
                for (Object next : expressionList) {
                    Expression expression = (Expression) next;
                    if (!(expression instanceof MapEntryExpression)) {
                        argumentList.add(expression);
                    }
                }
                if (!argumentList.isEmpty()) {
                    expressionList.removeAll(argumentList);
                    checkDuplicateNamedParams(elist, expressionList);
                    MapExpression mapExpression = new MapExpression(expressionList);
                    configureAST(mapExpression, elist);
                    argumentList.add(0, mapExpression);
                    ArgumentListExpression argumentListExpression = new ArgumentListExpression(argumentList);
                    configureAST(argumentListExpression, elist);
                    return argumentListExpression;
                }
            }
            checkDuplicateNamedParams(elist, expressionList);
            NamedArgumentListExpression namedArgumentListExpression = new NamedArgumentListExpression(expressionList);
            configureAST(namedArgumentListExpression, elist);
            return namedArgumentListExpression;
        } else {

名前付き引数は先に処理されるようだ。

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