Building Cocoa Applications: A Step by Step Guide

Building the GraphPaper Application

Now that we’ve thought about GraphPaper a bit, let’s get on with the work of building the application.

Changes to the Evaluator Back End

We need to make one change to Evaluator so that it can recognize more than a single expression on a line — that’s important, because GraphPaper will be sending (x,y) pairs such as (3,2*3+1) to Evaluator. (If we sent only y values, we might get confused.)

The easy way to do this is to make Evaluator recognize two expressions separated by a comma and terminated with a newline. Because we built Evaluator with lex and yacc, this change is easy to make and is confined to a single file, grammar.y.

1. Launch Project Builder, choose File → New Project, and double-click “Cocoa Application”.

2. Type “GraphPaper” in the Project Name field, hit the Tab key so that the project is saved in the folder ~/GraphPaper, and then click Finish.

3. Create a second target called Evaluator in the GraphPaper project by choosing PB’s Project → New Target menu command, double-clicking Tool at the bottom of the list in the resulting sheet, typing “Evaluator”, and clicking Finish in the second sheet in the project window.

4. Click the Files vertical tab in PB’s main window and disclose the Resources group.

5. Activate the Finder, open your ~/MathPaper folder, single-click grammar.y, and then Command-click rules.l to select these two files. We’ll add them to the GraphPaper project in the next step.

6. Drag the two-file selection from the Finder and drop it ...