Mini-project: A typed inventory

Coin Quest needs a reliable inventory before doors, shops, and persistence can ask what a player owns.

Use a dictionary from item names to numeric quantities. The add function owns updates; the query function turns an absent key into zero.

The ModuleScript returns only the focused API needed by callers.

--!strict asks Studio to check your code for type mistakes. It is an instruction for the editor and produces no Output message.

local is read as “local”: it creates a name that is available only in the current code scope.

end is read as “end”: it closes a block such as a decision, loop, or function.

return is read as “return”: it ends the current function call and sends a value to its caller.

{ } is read as “opening and closing braces”: it creates a table value around its entries.

[ ] is read as “opening and closing brackets”: it selects a table entry with an index or key.

A colon in a declaration, such as coins: number, introduces a type annotation: the kind of value that name is allowed to hold.

Read one statement at a time: name the value being read, what the operation does, and where its result goes. Keep identifiers exactly as written so you can find them again in the code.

Pause at calls, conditions, and loops. Explain when the body runs before moving to the next statement; use the line notes above when a symbol is unfamiliar.

Start with the statements outside function bodies. A function definition creates a callable value; its body runs when a call, event, or scheduled task reaches it.

Trace the arguments at each call and the branch or loop inside that call. Return to the caller when the function returns. For an event, use the action named in Try it to trigger the callback.

Line 3: The exported alias maps string keys to numeric quantities.

Line 5: The API table will hold focused functions.

Line 7: addItem names all three input roles.

Line 8: A missing item begins at zero.

Line 9: Negative additions are prevented.

Line 12: The query promises a number even for a missing key.

Line 16: The module returns its API without running side effects.

Before running, identify the starting values and any existing Studio objects this example needs. List what you expect to change.

After your practice change, check this result: The module returns predictable quantities for every disclosed case and exports no unrelated state.

Reading or printing a value leaves it unchanged. Look for assignments, calls that change state, and property updates to explain each change you observe.