Type Iteration (Loops)

Type Iteration with Loops

BambooBasic automatically maintains a list of all instances for each Type. You can iterate over all instances using special loop syntax.

For...EachIn Loop

The For...EachIn loop iterates through all instances of a Type:

Type TEnemy
    Field name:String
    Field health:Int
EndType

Function Main()
    ; Create some enemies
    Local goblin:TEnemy = Create TEnemy
    goblin\name = "Goblin"
    goblin\health = 30

    Local orc:TEnemy = Create TEnemy
    orc\name = "Orc"
    orc\health = 80

    Local dragon:TEnemy = Create TEnemy
    dragon\name = "Dragon"
    dragon\health = 500

    Print "=== All Enemies ==="

    ; Iterate through all TEnemy instances
    Local enemy:TEnemy
    For enemy EachIn TEnemy
        Print enemy\name & ": " & ToString(enemy\health) & " HP"
    Next

    Return False
EndFunction

Output:

=== All Enemies ===
Goblin: 30 HP
Orc: 80 HP
Dragon: 500 HP

For Each...In Loop (Alternative Syntax)

You can also use For Each...In syntax, which works identically:

Function Main()
    ; Create instances...
    Local goblin:TEnemy = Create TEnemy
    goblin\name = "Goblin"

    Local orc:TEnemy = Create TEnemy
    orc\name = "Orc"

    ; Alternative iteration syntax
    Local enemy:TEnemy
    For Each enemy In TEnemy
        Print enemy\name
    Next

    Return False
EndFunction

Note: Both For enemy EachIn and For Each enemy In work the same way. Use whichever you prefer!

Calling Methods During Iteration

Type TPlayer
    Field name:String
    Field score:Int

    Method AddScore(points:Int)
        this\score = this\score + points
    EndMethod

    Method ShowInfo()
        Print this\name & ": " & ToString(this\score) & " points"
    EndMethod
EndType

Function Main()
    ; Create players
    Local p1:TPlayer = Create TPlayer
    p1\name = "Alice"
    p1\score = 100

    Local p2:TPlayer = Create TPlayer
    p2\name = "Bob"
    p2\score = 250

    Local p3:TPlayer = Create TPlayer
    p3\name = "Charlie"
    p3\score = 175

    ; Give everyone bonus points
    Print "=== Adding Bonus Points ==="
    Local player:TPlayer
    For player EachIn TPlayer
        player\AddScore(50)
    Next

    ; Show results
    Print "=== Updated Scores ==="
    For player EachIn TPlayer
        player\ShowInfo()
    Next

    Return False
EndFunction

Output:

=== Adding Bonus Points ===
=== Updated Scores ===
Alice: 150 points
Bob: 300 points
Charlie: 225 points

Counting Instances

Function CountEnemies:Int()
    Local count:Int = 0
    Local enemy:TEnemy

    For enemy EachIn TEnemy
        count = count + 1
    Next

    Return count
EndFunction

Function Main()
    ; Create enemies
    Local e1:TEnemy = Create TEnemy
    Local e2:TEnemy = Create TEnemy
    Local e3:TEnemy = Create TEnemy

    Print "Total enemies: " & ToString(CountEnemies())  ; Output: 3

    ; Remove one
    Remove e2

    Print "After removal: " & ToString(CountEnemies())  ; Output: 2

    Return False
EndFunction

Removing During Iteration

Warning: Be careful when removing instances during iteration. The safe way is to mark them for removal:

Type TBullet
    Field x:Int
    Field y:Int
    Field isActive:Int

    Method Update()
        If this\isActive
            this\x = this\x + 5

            ; Mark as inactive if off-screen
            If this\x > 800
                this\isActive = False
            EndIf
        EndIf
    EndMethod
EndType

Function UpdateBullets()
    Local bullet:TBullet

    ; Update all bullets
    For bullet EachIn TBullet
        bullet\Update()
    Next

    ; Remove inactive bullets (separate pass)
    For bullet EachIn TBullet
        If bullet\isActive = False
            Remove bullet
        EndIf
    Next
EndFunction

Function Main()
    ; Create bullets
    Local b1:TBullet = Create TBullet
    b1\x = 700
    b1\isActive = True

    Local b2:TBullet = Create TBullet
    b2\x = 750
    b2\isActive = True

    Local b3:TBullet = Create TBullet
    b3\x = 100
    b3\isActive = True

    Print "Bullets before update: 3"

    UpdateBullets()

    ; Count remaining
    Local count:Int = 0
    Local b:TBullet
    For b EachIn TBullet
        count = count + 1
    Next

    Print "Bullets after update: " & ToString(count)  ; Should be 1

    Return False
EndFunction

Finding Specific Instances

Type TNpc
    Field id:Int
    Field name:String
    Field health:Int
EndType

Function FindNpcByName:TNpc(searchName:String)
    Local npc:TNpc

    For npc EachIn TNpc
        If npc\name = searchName
            Return npc  ; Found it!
        EndIf
    Next

    Return Null  ; Not found
EndFunction

Function FindNpcById:TNpc(searchId:Int)
    Local npc:TNpc

    For npc EachIn TNpc
        If npc\id = searchId
            Return npc
        EndIf
    Next

    Return Null
EndFunction

Function Main()
    ; Create NPCs
    Local npc1:TNpc = Create TNpc
    npc1\id = 1
    npc1\name = "Guard"
    npc1\health = 100

    Local npc2:TNpc = Create TNpc
    npc2\id = 2
    npc2\name = "Merchant"
    npc2\health = 50

    Local npc3:TNpc = Create TNpc
    npc3\id = 3
    npc3\name = "Blacksmith"
    npc3\health = 80

    ; Find by name
    Local found:TNpc = FindNpcByName("Merchant")
    If found <> Null
        Print "Found: " & found\name & " (ID: " & ToString(found\id) & ")"
    Else
        Print "NPC not found"
    EndIf

    ; Find by ID
    Local smithFound:TNpc = FindNpcById(3)
    If smithFound <> Null
        Print "Found: " & smithFound\name
    EndIf

    Return False
EndFunction

Processing Subsets

Type TUnit
    Field team:Int      ; 0 = enemy, 1 = ally
    Field health:Int
    Field name:String
EndType

Function DamageEnemies(amount:Int)
    Local unit:TUnit

    For unit EachIn TUnit
        If unit\team = 0  ; Only enemies
            unit\health = unit\health - amount
            Print unit\name & " takes " & ToString(amount) & " damage!"

            If unit\health <= 0
                Print unit\name & " defeated!"
            EndIf
        EndIf
    Next
EndFunction

Function HealAllies(amount:Int)
    Local unit:TUnit

    For unit EachIn TUnit
        If unit\team = 1  ; Only allies
            unit\health = unit\health + amount
            Print unit\name & " healed for " & ToString(amount) & " HP"
        EndIf
    Next
EndFunction

Function Main()
    ; Create mixed units
    Local enemy1:TUnit = Create TUnit
    enemy1\team = 0
    enemy1\name = "Goblin"
    enemy1\health = 50

    Local ally1:TUnit = Create TUnit
    ally1\team = 1
    ally1\name = "Knight"
    ally1\health = 100

    Local enemy2:TUnit = Create TUnit
    enemy2\team = 0
    enemy2\name = "Orc"
    enemy2\health = 80

    Print "=== Area Attack ==="
    DamageEnemies(30)

    Print ""
    Print "=== Healing Spell ==="
    HealAllies(25)

    Return False
EndFunction

Empty Lists

If no instances exist, the loop simply doesn't execute:

Function Main()
    ; No enemies created yet
    Local enemy:TEnemy

    Print "Checking for enemies..."

    For enemy EachIn TEnemy
        Print "Found: " & enemy\name
    Next

    Print "Search complete"  ; This will print even with no enemies

    Return False
EndFunction

Output:

Checking for enemies...
Search complete

Key Points

Use For variable EachIn TypeName to iterate all instances
Alternative syntax: For Each variable In TypeName
Declare the loop variable before the For loop
Each iteration gives you the next instance
Iteration order is creation order (first created to last created)
You can call methods and access fields during iteration
Be careful when removing instances during iteration
Empty lists result in zero iterations (not an error)

See Also

Custom Types - Defining Types
Type Instances - Creating and removing instances
Type Iteration (Keywords) - First, Last, Before, After, Insert
Control Flow - Other loop types

Examples

See the TypeIteration.bam example for complete demonstrations.