[TYPO3-dev] Another TypoScript looping solution

[Davide Principi]

Hi all,
I've read about the `.split`-based looping techniques in TypoScript and 
I'd like to share another TypoScript looping solution exploiting CASE, 
registers, current-value and recursive calls that I'm applying to my 
TS-templates.

I state that what I'd been searching for was an extensible fallback 
mechanism to generate a thumbnail image, trying a list of methods until 
one generates the image successfully (attached image, default image, 
text image...).

The solution has

a) the list of image generating methods to attempt

b) the recursive call to the next method

c) the exit condition

An outline of the TypoScript code follows (don't cut&paste it):


lib.recursiveLoop = CASE
lib.recursiveLoop {

	key {
		#
		# (a) use a register to hold the list or methodX
		# if empty
		#
		data = register : iterations
		ifEmpty = methodX
		split {
			token = ,
			returnKey.current = 1
		}
	}



	method1 =< ...
	method2 =< ...
	.
	.
	.
	methodN =< ...

	#
	# As a last resort we MUST return a non-empty value to avoid
	# an infinite loop!
	#
	default = TEXT
	default.value = ...


	#
	# (c) the next condition (otherwise terminates)
	#
	stdWrap.ifEmpty {

		#
		# (b.1) Increment the list pointer, stored in the
		# current-value:
		#
		setCurrent {
			current = 1
			stdWrap.wrap = |+1
			prioriCalc = 1
		}

		#
		# (b.1) Recursive call
		#
		cObject =< lib.recursiveLoop
	}
}


To start a loop that selects a subset of available methods we have to 
load the "iterations" register. We must also ensure that the 
current-value is 0:

lib.callLoop1 = COA
lib.callLoop1 {
	10 = LOAD_REGISTER
	10.iterations = method3,method5

	20 = TEXT
	20 {
		setCurrent = 0
		cObject =< lib.recursiveLoop
	}

	30 = RESTORE_REGISTER
}



That's all: I hope you like it.


-- 
Davide Principi - http://www.docweb.provincia.pu.it/

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