The Component Selection Tool allows you to find an existing component for reuse. This can be either on the basis of its type, or by ‘diving down’: following links through other elements, e.g. from a graph, to an object in that graph, to an object included as a property. This is particularly useful if the object you want to attach has not yet been loaded, in which case it will not appear in lists of objects of the specified type.

The list on the left initially shows all objects of the required type and its subtypes (if no elements of that type are currently loaded, you will be warned and the list will show all loaded graphs, from which you can Dive down: see below).

If the object you want to reuse is visible:

When an object is selected on the left, the Contents list on the right shows the objects it contains or refers to (e.g. as properties). From either list you can dive down (Dive in the popup menu), filling the left hand list with the contents of the selected object. You can also jump Back one level, or Edit... or view the Info... for the selected object.

Items that are of the required type are shown in the normal font: double-clicking them is the same as choosing Select & OK. Items not of the selected type are shown in an italic font: double-clicking is the same as choosing Dive.

For more comprehensive browsing the Component Selection Tool offers navigation buttons at the top of the window. The Graphs button fills the left-hand list with all available graphs, allowing you to dive down to an object you know is contained in a certain graph. My Instances changes back to showing instances of the required type. Other Instances allows you to browse instances of another type. For example, if you want to reuse a Parameter, and you know it is contained in a certain Operation in a certain Class, you can view all Classes with this button, then dive down via the Operation to the Parameter you want. The Load button loads more objects from the repository (see Section 3.1.2).

The Selection History pull-down list allows you to jump quickly back to a place from which you have previously chosen objects in this tool.

In situations where you can select multiple elements for reuse the tool looks slightly different (Figure 3-37). It works as described above, with the exception that you collect the objects you want into the ‘Already selected’ list on the right by selecting them in another list and choosing Add (or double-clicking them). Objects can also be removed from the ‘Already selected’ list from its menu. If you only want one object, you can add it and close the dialog in one operation with Add & OK.