Using Objective-C Metadata to Generate Class Dependency Graph

Question

This guy came up with a pretty neat tool to generate a class dependency graph - however, it relies on parsing your source code and looking for #import directives.

• http://seriot.ch/blog.php?article=20110124
• https://github.com/nst/objc_dep/blob/master/objc-dep.py

This is neat, but I have a number of problems with this. Not least of which is it doesn't take into account imports of imports nor prefix headers nor whether-or-not the class(es) in the file referenced by the import are actually being used.

I'd like to do something more akin to class-dump and examine the Objective-C metadata stored in the Mach-O file to generate an in-memory representation of the class dependencies.

I'd rather not do this from scratch, so I'm wondering:

• Has it already been done?
• Is there an open-source library which would provide me with the foundational tools I need to extract this information (a library which examines the Mach-O file and creates a façade of the Objective-C information contained within - such that I could iterate over all of the classes, their methods, properties, ivars, etc and scan for references to other classes) I figure class-dump's source would be a good place to start.
• If you have experience in this sort of thing, is what I'm trying to accomplish feasible?
• What roadblocks will I need to overcome?

Answer 1

Has it already been done?

Not that I know of.

Is there an open-source library which would provide me with the foundational tools I need to extract this information?

At the core of class-dump is libMachObjC which does exatly what you want, i.e. parse all classes/methods/ivars and more. The API is very clean, it should be very easy to use.

If you have experience in this sort of thing, is what I'm trying to accomplish feasible?

Unfortunately, no because some classes don't declare the real class but use id instead. For example, here is the information that can be extracted from a class-dump of UIKit:

@interface UITableView : UIScrollView <NSCoding>
{
    int _style;
    id <UITableViewDataSource> _dataSource;
    id _rowData;
    ...

The _rowData ivar type information is id but if you check at runtime you will see that _rowData is an instance of the UITableViewRowData class. This information is not present in the Mach-O binary so you have no way to find the relation between UITableView and UITableViewRowData. The same applies for method parameters.

Answer 2

Here's a solution that relies on information in mach.o files, and generates graph dependency based on that information: https://github.com/PaulTaykalo/objc-dependency-visualizer