Ebook: Practical object-oriented design: an agile primer using Ruby

Object-oriented programming languages exist to help you create beautiful, straightforward applications that are easy to change and simple to extend. Unfortunately, the world is awash with object-oriented (OO) applications that are difficult to understand and expensive to change. Practical Object-Oriented Design, Second Edition, immerses you in an OO mindset and teaches you powerful, real-world, object-oriented design techniques with simple and practical examples. Sandi Metz demonstrates how to build new applications that can "survive success" and repair existing applications that have become impossible to change.;Object-oriented design -- Designing classes with a single responsibility -- Managing dependencies -- Creating flexible interfaces -- Reducing costs with duck typing -- Acquiring behavior through inheritance -- Sharing role behavior with modules -- Combining objects with composition -- Designing cost-effective tests.