Concepts - Cascading Lists
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Cascading lists are a hierarchical set of lists where the first list entry chosen (called the parent) defines which subsequent lists (called children) are offered. The word cascade refers to the way a child can become a parent to another child and so on. Most lists do not cascade, quite a few have 1 level of cascade and some really complicated ones have 2 or 3. |
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A good example of a cascading list one that is used to identify a motor vehicle. This could be set up as one list containing every possible model of vehicle arranged in alphabetical order. The device user would need to scroll through everything to get to (for example) Volkswagen Tiguan. They would then need to scroll through individual entries for each of the 4 available models and, of those, each of the 11 available engines. If the customer changed their mind about the model, or even just the engine size, the whole process would need to be repeated. Cascading lists would enable the device user to select a Vehicle Manufacturer ("Volkswagen") from a drop-down list. magic5 would then look for the list indentified as the child for the "Volkswagen" list entry and make it available in the drop-down list that has been specified on the template as the child of the Vehicle Manufacturer drop-down list (called, for instance, Series). From the Series list the device user could choose "Tiguan" and magic5 would find the child list for "Tiguan" to use in the drop-down list specified as a child of Series (a list called, for instance, Model) and from here the device user could choose "Match" which would result in a list of available engine sizes appearing in a further list identified as the child of Model list entry called Match. |
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Initial set-up time is well spent as it not only helps the device user to navigate on a small-screened device but reduces the likelihood of errors and allows them to change any selection in the hierarchy knowing that the rest of the lists will be amended accordingly. |
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To make this work on a template, two list Item types (most commonly drop-down list) need to be linked through the 'unique name' of parent item in the Advanced tab. If subsequent levels are required, the unique name of the first child list becomes the named parent list of the next level. In the above example
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See Also