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42 lines
1.1 KiB
Markdown
42 lines
1.1 KiB
Markdown
# Sources
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*Sources* in Vide are special objects that store a single value. They are the
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core of reactivity in Vide. Each source represents a source of data, and they
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can be composed and derived to create new sources of data.
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A source in Vide can be created using `source()`.
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```lua
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local source = vide.source
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local count = source(0)
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```
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The value passed to `source()` is the initial value of the source.
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The value of a source can be set by calling it with an argument, and can be read
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by calling it with no arguments.
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```lua
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count(count() + 1) -- increment count by 1
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```
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Sources can be *derived* by wrapping them in functions. A wrapped source
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effectively becomes a new source.
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```lua
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local count = source(0)
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local text = function()
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return "count: " .. tostring(count())
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end
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print(text()) -- "count: 0"
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count(1)
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print(text()) -- "count: 1"
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```
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Derived sources should be pure functions. This is where the same output is
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always produced for the same input. As well as making source updates more
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predictable, knowing that updates are pure allows Vide to use optimizations such
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as caching, to avoid updating derived sources if their inputs are the same.
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