The For Objects
Often when building UI, you need to deal with lists, arrays and tables. For example:
- creating an array of TextLabels for a player list
- generating a settings page from pairs of keys and values in a configuration
- filling a grid with inventory slots and items
Most of these use cases involve processing one table into another:
- converting an array of player names into an array of TextLabels
- converting a table of settings into a table of UI controls
- converting an array of inventory items into an array of slot UIs
So, to assist with these use cases, Fusion has a few state objects which are
specially designed for working with arrays and tables. These are known as the
To start, let's try making a player list using the basic state objects from before. Let's define a changeable list of player names and some basic UI:
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Now, let's make a
Computed which generates that list of text labels for us:
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This is alright, but there are a few problems:
- Firstly, there's a fair amount of boilerplate - in order to generate the list
of text labels, you have to create a
Computed, initialise a new table, write a for-loop to populate the table, then return it.
- Boilerplate is generally annoying, and especially so for a task as common as dealing with lists and tables. It's less clear to read and more tedious to write.
- Secondly, whenever
playerNamesis changed, you reconstruct the entire list, destroying all of your instances and any data associated with them. This is both inefficient and also causes issues with data loss.
- Ideally, you should only modify the text labels for players that have joined or left, leaving the rest of the text labels alone.
To address this shortcoming, the
For objects provide a cleaner way to do the
same thing, except with less boilerplate and leaving unchanged values alone:
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Over the next few pages, we'll take a look at three state objects:
ForValues, which lets you process just the values in a table.
ForKeys, which lets you process just the keys in a table.
ForPairs, which lets you do both at the same time.