MacroExpander Class

Detailed Description

Variables

Variable names can be basically any string without dollar sign and braces, though it is recommended to only use 7-bit ASCII without special characters and whitespace.

If there are several variables that contain different aspects of the same object, it is convention to give them the same prefix, followed by a colon and a postfix that describes the aspect. Examples of this are CurrentDocument:FilePath and CurrentDocument:Selection.

When the variable manager is requested to replace variables in a string, it looks for variable names enclosed in %{ and }, like %{CurrentDocument:FilePath}.

Environment variables are accessible using the %{Env:...} notation. For example, to access the SHELL environment variable, use %{Env:SHELL}.

Providing Variable Values

Plugins can register variables together with a description through registerVariable(). A typical setup is to register variables in the Plugin::initialize() function.

bool MyPlugin::initialize(const QStringList &arguments, QString *errorString)
{
    [...]
    MacroExpander::registerVariable(
        "MyVariable",
        Tr::tr("The current value of whatever I want."));
        [] {
            QString value;
            // do whatever is necessary to retrieve the value
            [...]
            return value;
        }
    );
    [...]
}

For variables that refer to a file, you should use the convenience function MacroExpander::registerFileVariables(). The functions take a variable prefix, like MyFileVariable, and automatically handle standardized postfixes like :FilePath, :Path and :FileBaseName, resulting in the combined variables, such as MyFileVariable:FilePath.

Providing and Expanding Parametrized Strings

Though it is possible to just ask the variable manager for the value of some variable in your code, the preferred use case is to give the user the possibility to parametrize strings, for example for settings.

(If you ever think about doing the former, think twice. It is much more efficient to just ask the plugin that provides the variable value directly, without going through string conversions, and through the variable manager which will do a large scale poll. To be more concrete, using the example from the Providing Variable Values section: instead of calling MacroExpander::value("MyVariable"), it is much more efficient to just ask directly with MyPlugin::variableValue().)

User Interface

If the string that you want to parametrize is settable by the user, through a QLineEdit or QTextEdit derived class, you should add a variable chooser to your UI, which allows adding variables to the string by browsing through a list. See Utils::VariableChooser for more details.

Expanding Strings

Expanding variable values in strings is done by "macro expanders". Utils::AbstractMacroExpander is the base class for these, and the variable manager provides an implementation that expands Qt Creator variables through MacroExpander::macroExpander().

There are several different ways to expand a string, covering the different use cases, listed here sorted by relevance:

• Using MacroExpander::expandedString(). This is the most comfortable way to get a string with variable values expanded, but also the least flexible one. If this is sufficient for you, use it.
• Using the Utils::expandMacros() functions. These take a string and a macro expander (for which you would use the one provided by the variable manager). Mostly the same as MacroExpander::expandedString(), but also has a variant that does the replacement inline instead of returning a new string.
• Using Utils::CommandLine::expandMacros(). This expands the string while conforming to the quoting rules of the platform it is run on. Use this function with the variable manager's macro expander if your string will be passed as a command line parameter string to an external command.
• Writing your own macro expander that nests the variable manager's macro expander. And then doing one of the above. This allows you to expand additional "local" variables/macros, that do not come from the variable manager.