Transfer practice · Compare two item tables by their name and quantity fields, not their identities. Return false when either field differs.

Copy a nested loadout safely: practice

v3 · Activity 1 of 1 · table-identity · references · nested-tables · 12 min Runs here

Chapter outline

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Mini-mission

Use a familiar idea in a different task. Read the changed requirement before running.

Your task

Compare two item tables by their name and quantity fields, not their identities. Return false when either field differs.

Interface: previewLoadout(saved:{tools:{string}},extra:string) -> summary table

Input	Expected
Equal-looking separate tables`{ name = "Lamp", quantity = 2 }, { name = "Lamp", quantity = 2 }`	`true`
Different quantity`{ name = "Lamp", quantity = 2 }, { name = "Lamp", quantity = 3 }`	`false`

See another example

local saved = { tools = {"Hammer"} }
local preview = table.clone(saved)
preview.tools = table.clone(saved.tools)
table.insert(preview.tools, "Brush")
return { originalCount = #saved.tools, previewCount = #preview.tools }

Copying both the outer table and the tools sequence lets the preview change independently.

Syntax in this activity

New syntax: table.clone()

Earlier ideas used here

tables
dictionaries
table-insert

Your explanation

Self-check rubric

Explain why assigning a table shares its identity.
Identify the nested tools layer that remains shared after only the outer clone.
Predict the originalCount before and after cloning the tools sequence; use evaluated output to check.

Your explanation is a self-check. Exact wording is not automatically graded.

Explain more

Assigning local preview = original gives both names the same table. It does not duplicate contents. Two separately created tables with equal-looking contents are different identities.

table.clone makes a shallow copy. Nested tables inside the copy still refer to the original nested tables.

Copy only the nested layer you plan to change for this activity. Arbitrary deep copying needs policies for cycles, functions and special engine values; this small example does not claim to solve all of them.

Explain this code

Select a word or symbol in this authored example. Your editor draft stays unchanged.

  previewLoadoutsaved, extra
     preview  table.clonesaved
    table.insertpreview.tools, extra
      originalCount  saved.tools, previewTools  preview.tools 

 previewLoadout

Choose a highlighted part to see what it means.

Free experiment

This is a private experiment copy. It does not replace your answer or complete the activity.

These inputs apply when your scratchpad returns the function described by the activity interface.

Test different inputs

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local saved = { tools = {"Hammer"} }
local preview = table.clone(saved)
preview.tools = table.clone(saved.tools)
table.insert(preview.tools, "Brush")
return { originalCount = #saved.tools, previewCount = #preview.tools }

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Experiment Output

Your output will appear here.

Reset starter

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Code

Luau

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local function sameItem(first, second)
    return first == second
end
return sameItem

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Your output will appear here.

Ready

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Your task

Compare two item tables by their name and quantity fields, not their identities. Return false when either field differs.

Interface: previewLoadout(saved:{tools:{string}},extra:string) -> summary table

Input	Expected
Equal-looking separate tables`{ name = "Lamp", quantity = 2 }, { name = "Lamp", quantity = 2 }`	`true`
Different quantity`{ name = "Lamp", quantity = 2 }, { name = "Lamp", quantity = 3 }`	`false`

See another example

local saved = { tools = {"Hammer"} }
local preview = table.clone(saved)
preview.tools = table.clone(saved.tools)
table.insert(preview.tools, "Brush")
return { originalCount = #saved.tools, previewCount = #preview.tools }

Copying both the outer table and the tools sequence lets the preview change independently.

Syntax in this activity

New syntax: table.clone()

Earlier ideas used here

tables
dictionaries
table-insert

Your explanation

Self-check rubric

Explain why assigning a table shares its identity.
Identify the nested tools layer that remains shared after only the outer clone.
Predict the originalCount before and after cloning the tools sequence; use evaluated output to check.

Your explanation is a self-check. Exact wording is not automatically graded.

Explain more

Assigning local preview = original gives both names the same table. It does not duplicate contents. Two separately created tables with equal-looking contents are different identities.

table.clone makes a shallow copy. Nested tables inside the copy still refer to the original nested tables.

Explain this code

Select a word or symbol in this authored example. Your editor draft stays unchanged.

  previewLoadoutsaved, extra
     preview  table.clonesaved
    table.insertpreview.tools, extra
      originalCount  saved.tools, previewTools  preview.tools 

 previewLoadout

Choose a highlighted part to see what it means.

Free experiment

This is a private experiment copy. It does not replace your answer or complete the activity.

These inputs apply when your scratchpad returns the function described by the activity interface.

Test different inputs

Font size Plain text

local saved = { tools = {"Hammer"} }
local preview = table.clone(saved)
preview.tools = table.clone(saved.tools)
table.insert(preview.tools, "Brush")
return { originalCount = #saved.tools, previewCount = #preview.tools }

Luau keyword highlighting · Ctrl/⌘ + Enter: Run · Esc: leave editorTab inserts indentation

Experiment Output

Your output will appear here.