ObjectPool

ObjectPool

Description

Holds a collection of pooled objects and handles creating new ones when the pool is empty.

Functions

• clear
• getLength
• getOrCreateNext
• new
• returnToPool

clear

Description

Removes all instances from the pool's collections.

Definition

clear()

Code

function ObjectPool:clear()
    table.clear( self.poolSet)
    table.clear( self.pool)
end

getLength

Description

Gets the total count of objects in the pool.

Definition

getLength()

Return Values

any	count	The number of items in the pool.

Code

function ObjectPool:getLength()
    -- TODO:Replace with __len metafunction in Lua 5.2
    return # self.pool
end

getOrCreateNext

Description

Gets and returns an instance from the pool, or creates one if the pool is empty.

Definition

getOrCreateNext()

Return Values

any	instance	The pooled or created object.

Code

function ObjectPool:getOrCreateNext()

    -- Get the next object in the pool.
    local instance = table.remove( self.pool)

    -- If there was no object in the pool, create a new one.
    if not instance then

        -- If the constructor is the default empty table, skip the unpacking.
        if self.objectConstructor = = ObjectPool.EMPTY_TABLE_CONSTRUCTOR then
            instance = self.objectConstructor()
            -- Otherwise; unpack the arguments and call the constructor.
        else
                instance = self.objectConstructor( table.unpack( self.objectConstructorArguments, 1 , self.objectConstructorArguments.n))
            end
            -- Otherwise; also remove the object from the set.
        else
                self.poolSet[instance] = nil
            end

            -- Return the created or gotten object.
            return instance
        end

new

Description

Creates a new object pool with the given constructor.

Definition

new(function? objectConstructor, any ...)

Arguments

function?	objectConstructor	The constructor function to call in order to create new objects when the pool is empty. If this is nil, ObjectPool.EMPTY_TABLE_CONSTRUCTOR will be used.
any	...	The arguments to pass through to the constructor.

Return Values

any	instance	The created instance.

Code

function ObjectPool.new(objectConstructor, .. .)

    -- Ensure a constructor was given or is nil.
    --#debug Assert.isNilOrType(objectConstructor, "function", "Object constructor was not a function or nil!")

        -- Create the instance.
        local self = setmetatable( { } , ObjectPool _mt)

        -- The object constructor and arguments.
        self.objectConstructor = objectConstructor or ObjectPool.EMPTY_TABLE_CONSTRUCTOR
        self.objectConstructorArguments = table.pack( .. .)

        -- The pool of objects.
        self.pool = { }

        -- The set of pooled objects to avoid duplicates.
        self.poolSet = { }

        -- Return the created instance.
        return self
    end

returnToPool

Description

Returns the given instance to the pool.

Definition

returnToPool(table instance)

Arguments

table	instance	The instance to return to the pool.

Code

function ObjectPool:returnToPool(instance)

    -- Ensure the given instance exists.
    if instance = = nil then
        return false
    end
    --#debug Assert.isType(instance, "table", "Given instance was not a table!")

    -- Ensure the object is not already pooled.
    if self.poolSet[instance] ~ = nil then
        return false
    end

    -- If the object constructor is the default empty table, clear the table.
    if self.objectConstructor = = ObjectPool.EMPTY_TABLE_CONSTRUCTOR then
        table.clear(instance)
        -- Otherwise; if the instance has a reset function, call it.
        elseif instance.reset ~ = nil then
                instance:reset()
            end

            -- Add the object to the collections.
            table.insert( self.pool, instance)
            self.poolSet[instance] = instance

            -- Return true, as the addition was a success.
            return true
        end