Sometimes (many times!) code does not compile properly, as you can see in the PB window in Figure 5-27.

Figure 5-27. Compiler errors in PB’s main window

If instead of a clean compile you get compiler warning or error messages, you have probably made a typographical error at some point in the code. For example, the error message in Figure 5-27 was generated by removing the first semicolon from the displayX method in the Controller.m file (the semicolon is missing from the statement above the highlighted statement at the bottom in Figure 5-27).

If you click on an error message in the top-right panel of PB’s window (e.g., “syntax error, found ’setStringValue’”), the offending line of code will be highlighted in the source code file, Controller.m. If you double-click the error message, a new window will open with the line containing the error highlighted (actually, the error is in the previous line, but it doesn’t cause a problem until the highlighted line). This is a great help in finding and fixing compiler errors!

If you get compiler errors for source code that you type in from this book, we suggest that you first reexamine your code line by line, rather than downloading our code from the Web. Examining code for errors is an important skill to develop.

As an alternative to double-clicking an error message, you can open the Controller.m file in a PB editor window, type Command-L to bring up the Goto panel, enter “45” (the line where the error was reported), and inspect the code on line 45 and previous lines.

(If you compiled your program from within GNU Emacs, you can use the Emacs command “goto-next-error” to automatically jump to the file and line containing the error.)