APIs to read and set page variables: the values a page defines with ${name = …} and page-lua blocks.

Each function takes an optional page name as its last argument. Without it they use the page the running code is on: the page a ${…}, code widget or button belongs to (for a button inside a transclusion, the transcluded page), or else the open page.

Example: ${counter = 1} Counter * pi: ${math.pi * counter}

${widgets.button("Add one", function() pageVars.set("counter", counter + 1) end)}

API

pageVars.get(name, page?)

Returns one of a page's variables. A name the page doesn't define is an error; a variable holding nil returns nil.

pageVars.get("salary", "Budget")
pageVars.get("rate")

pageVars.all(page?)

Returns a read-only table of all of a page's variables, which you can print or iterate.

pageVars.all("Budget")
for name, value in pairs(pageVars.all()) do print(name, value) end

An expression that reads a page’s variables updates when they change. Reading a page whose definitions fail is an error naming the first failing definition, and a chain of pages that read each other is reported as a cycle.

pageVars.set(name, value, page?)

Sets a variable by rewriting its ${name = …} in the page text, so the page shows and saves the new value and everything that uses it updates.

pageVars.set("rate", 0.2)
pageVars.set("salary", 600, "Budget")

• value must be a number, string, boolean, nil, or a table of these (tables may nest). A function, a table with a metatable, or a table that contains itself is an error.
• The page must define name with exactly one ${name = …} holding a plain value or a table literal of plain values. A formula such as ${total = a + b}, a variable assigned only in a page-lua block, or a name the page doesn't define is an error.
• A table is written back pretty printed: list items first, one per line, then named fields. Continuation lines follow the cell's indentation.
• On the open page, the change is a single undoable edit and the page is saved right away.
• Setting a variable to the value it already has changes nothing.
• A read-only space, or a read-only target page, is an error.