CSC/ECE 517 Fall 2014/ch1a 11 ap

Introduction: Automated Refactoring Techniques for AppCode

AppCode is an Integrated Development Environment (IDE) for Objective-C,C, C++, and JavaScript development built on JetBrains’ IntelliJ IDEA platform, which is built on Java. Users can extend its abilities by either installing plug-ins created for IntelliJ Platform, or they can write their own plug-ins.Media:books.png

Code refactoring is the process of restructuring existing computer code – changing the factoring – without changing its external behavior. Many a times, we face the need to change the name of a variable in our code- mostly because we find another one better suited for its functionality. Doing this manually can be time consuming & often leads to many mistakes. That is why, many new IDEs (Integrated Development Environments) come with inbuilt functions for refactoring. As you read further, you will know that refactoring is not limited to changing variable name. There are many things IDEs allow programmers to do to edit their code. These changes are not logical, in the sense that they do not make any change to functionality or behavior of the program; but are needed to improve code in terms of understanding & user friendliness.

Background

"By continuously improving the design of code, we make it easier and easier to work with. This is in sharp contrast to what typically happens: little refactoring and a great deal of attention paid to expediently adding new features. If you get into the hygienic habit of refactoring continuously, you'll find that it is easier to extend and maintain code." —Joshua Kerievsky, Refactoring to Patterns

Refactoring improves nonfunctional attributes of the software. Advantages include improved code readability and reduced complexity to improve source code maintainability, and create a more expressive internal architecture or object model to improve extensibility. To help programmers easily improve code design as it evolves over time, AppCode provides a solid set of reliable code refactorings. These include vital ones like Rename, Extract Method, Introduce Variable and Inline, as well as more powerful ones, e.g. Extract Block Parameter/Protocol/Category/Superclass, Change Signature, Convert Method to Function and back, Pull Members Up/Push Members Down, and others. First public preview version of AppCode became available in April 2011. The latest stable release is version 3.0 and is available at JetBrains’ official web site.

Features of AppCode

Finest coding assistance Context-aware editor gives you precise code completion choices due to deep understanding of your code structure, saves you from unnecessary typing by generating code, allows you to program by intention and minimize the routine tasks. AppCode automatically imports a class if it is not imported by the programmer in the code. Parameter Info(ctrl+P) assists the programmer in determining what exact parameters need to be passed to a method or function. Code reordering allows you to order your code. For example, to move block of code up or down, the following commands can be used:Cmd+Shift+Up/Down and for lines of code: Alt+Shift+Up/Down. Such assistance allows user to concentrate more on the logic of program than its structure.

Reliable refactorings Safe, accurate and reliable refactorings in AppCode allow you to modify and improve your code at any time. Whether you need to revive old code base, or brush up the project structure, you can always lean on AppCode. Various refactoring techniques mentioned below make it easy to refactor code.

Fast project navigation Navigations from a method to its declaration or any of its usages, through classes hierarchy or from one file to another are very easy to follow. Programmer can jump to any file, class, or symbol in your project in no time, or see all real usages of a symbol, not just text matches.

Code quality tracking On-the-fly code quality analysis for Objective-C, C, C++, JavaScript, CSS, HTML, XML and Xpath is done in AppCode. AppCode saves you from potential errors, and gives you hints when your code can be improved. Moreover, it comes with integrated Clang Static Analyzer.

Powerful debugger Programmers can fine-tune apps or unit tests using a convenient debugger with flexible breakpoints, watches, frames view and evaluate expressions. With the help of conditional breakpoints in AppCode, one can have more control over the debugging process, and an option to log an evaluated message when a breakpoint is hit.

Seamless integrations AppCode seamlessly integrates with the most popular version control systems, like Git, Mercurial, Perforce, etc.; Kiwi testing framework, Dash and Ingredients documentation tools, a number of issue trackers and provides 100% interoperability with Xcode. AppCode is also integrated with Reveal , a fantastic tool from Itty Bitty Apps that helps debug iOS applications. You can experience the benefits of this tool right from AppCode, including the ability to inspect view elements and hierarchies of your iOS apps in real time, use the 2D and 3D visualization possibilities, and apply the view's editing on the fly, which is a convenient way to tweak the interface without recompiling.

Refactoring Techniques in AppCode:

Automated Techniques used by AppCode are listed below:

Rename

By using this, one can rename a file, class, method, property, ivar, local variable, and so on. In the file or project view, the shortcut triggers renaming a file or a class. If you just are renaming a file (such as a plist or an image), AppCode will rename the file, and also change where it is referenced. If you are renaming a class, both the header, and the implementation of the class is renamed, and the references of the files in the project file. If you select Rename when the cursor is on a class name used by the class, the selected class is renamed. If you triggers the rename from inside the source file, the name of the class, variable, and so on, is entering a “edit mode,” like “Edit all in Scope,” in Xcode. The difference is that while in Xcode you renamed only the names inside the current class.

Change Signature

Often, a programmer needs to alter a method signature. This can be to include an additional argument, or maybe the argument is not needed anymore, or even the order of the arguments is not right. If the method is called from several places, this can be a time-consuming and error prone task. By using AppCode, this is done in a simple and safe way. This is a really powerful feature in AppCode. You can also change the return type, and even convert a method to a function or a block, or vice versa.

Convert

Converting a method to a function or a block can also be done by using one of the Convert to menu items. In addition to these, you also have Convert to Property and Convert to Instance Variable.

Move

Sometimes, a method may be defined in the wrong class. The Move refactoring tehnique allows you to move a property, variables and methods from one class to another. If the target class does not exist, you get a warning that tells you that. Once the method is moved, the previous parameters that were being sent to the method need to be cleaned up and it should be checked whether additional data needs to be passed over now via the method invocation.

Copy

When in the project browser, selecting a header, or an implementation file, or when inside one of these files, F5 will prompt you to enter the name of the new copy of the files, and where to copy them. While in the “To directory” input field ⌃␣ will provide path completion. When accepting, the class name inside the source files is changed as well.

Safe Delete

While deleting a class or a file, the programmer checks if that class or file is being used anywhere else in the program. Using Safe Delete, the programmer can be warned of any such multiple usages through a warning message. The search is also extended to comments and strings.

Extract

To quickly move code around in a full swing of refactoring, one can extract an expression to a variable or extract a full code block into a new method, and add a parameter to it using Introduce Parameter refactoring.

For refactoring, command Ctrl+T can be used to see what refactorings are suitable for the current context. The new Move refactoring allows you to move any class or member, or even a top level element, say a namespace through your project. Not only will AppCode move an element, but it will update the references, automatically manage imports and escalate visibility if needed.

There are several Extract factoring’s, and here is a short description of each:

Extract Variable Let say that you have a hard coded value. You select the value, and type ⌥⌘V. AppCode will declare a variable above where it’s used, with the correct type, and the name of the new variable selected. To change the proposed name, just begin to type the name of the variable. If no value or expression is explicitly selected, AppCode gives you a suggestion of what to base the value of the introduced value from.

Extract Constant This refactoring is similar to Extract Variable, but this introduces a constant instead. If no actual value is selected, AppCode gives you an opportunity to select what the constant is based on from values and expressions in scope. When the constant is selected, AppCode asks for you if you would like to replace only this one, or all similar values found in the current file.

Extract Parameter If you are creating a variable inside a method, but you would like it to be passed as a parameter, Extract parameter, ⌥⌘ P is the refactoring you would like to use.

Extract Property By using ⌥⌘E on a variable, AppCode shows a dialog where the declaration of the property is shown, togheter with a checkbox. If you check the checkbox, the property is generated in a private category. If not, the property is declared in the header.

Extract Instance Variable By using ⌥⌘I on a local variable, AppCode changes it into an ivar, but with the option to generate a property for the variable if the checkbox is selected. You can also select to declare the ivar in the interface (which you don’t want to do).

Extract Define ⌥⌘F extracts a macro from the selected value or expression

Extract Typedef As the name suggests, ⌥⌘F creates a typdef from the selected type. Extract Method This is one of the most my frequently used refactoring. Let say a method has too much responsibility, and you want to move some of the logic into a new method, Select the code you want to move, type ⌥⌘F, and AppCode generates a new method for you, including necessary parameters.

Extract Block Parameter By using Extract Block Parameter you select a chunk of code. A block declaration based on the selected code is created, and the signature of the method is changed to take a block of this type. Finally, the existing usages of this method are changed so that the extracted block is passed as a parameter.

Extract Superclass To create a superclass from an existing class, the easiest way to accomplish this is to select the Extract Superclass. This refactoring does not have a default keyboard shortcut (You can create one yourself). You will be presented with a dialog where methods, properties, and ivars are shown in a list with checkboxes, and an input field where you type the name of the new superclass. You check the name of what you want to move into the new superclass. If one of the selected methods has dependencies to other methods, properties, or ivars, you get a warning, telling you about the problem.

Extract Subclass Here you create a subclass from a superclass. You select which methods, ivars and properties you want to take with you into the new subclass. Extract Protocol and Category Similar to the two above, except you are extracting protocols and categories.

Inline

If you want to inline a method, AppCode will move the implementation of the method into where it’s called from. If the method is called from more than one place, AppCode prompts you and asks for “Do you want to inline ‘n’ usages of method ‘mehodName’? You options are: cancel the refactoring, execute the operation or view usages of the method you have selected to inline. If you select the latter, a list of usages is shown, and while navigating in this list, you can exclude the calls you don’t want to inline