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Variables can be used throughout Continua and created at certain levels in the hierarchy. Environment variable are there by default and cannot be changed, they're the last variable namespace checked when determining a variable's value. The next level of variables checked at the Application level which is the highest level a user can define a variable. A variable defined in the Application namespace can be used anywhere in Continua. The next level of variables are for projects which are defined on the project wizard page followed by configuration variables which are on the configuration wizard page. The final variable namespace and the one at the top of the hierarchy is the Build Namespace. There are 3 ways to define a build level variable. When a build is triggered (defined when creating the trigger), when manually starting a build that prompts for variables and when setting a variable in a stage using the Set Variable Action. Variables can have a value type of Text, Numeric or Expression. Expression variables can contain references to other variable or objects. Variables can later be referenced using the Objects and Expressions Syntax.
The values of Application, Project and Configuration variables cannot be modified during a build, whatever they're set to when the build starts is what they will always be. To access those variables using the query syntax explained below you would prefix the variables with the name space. Eg. %Application.MyVariable%, %Project.MyVariable%, %Configuration.MyVariable%. Alternatively, you can choose to not specify a name space for a variable in which case it will try and get the value for that variable searching namespaces from the top down. Not prefixing your variable with a namespace is the only way to access build namespace variable values. It's also a simple way to allow name spaces to override their parents, for example when defining a project level variable then creating an override in a particular configuration within that project, you could just type %MyVariable% and the value would resolve to a different value depending on the Configuration it was used in.
Objects & Expressions
Throughout Continua you will come across input fields which accept Expressions in their value. Expressions are built up at design time then evaluated at run time. An Expression can reference a Continua Variable or a Continua Object. The UI differentiates these two types by starting and ending an Expression with the "%" character for variables and a "$" character for objects, these two keys will be referred to as "starting keys". A Variable Expression would look something like "%Configuration.MyOwnVariable%" and an Object Expression would look something like "$Build.BuildNumber$". To determine if an input field accepts Expressions as values, press a starting key and wait for the auto-complete drop down to appear below the input field.
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