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How to use looping (recursive) workflows in Bubble.io

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Summary

Core Theme

Recursive or looping workflows enable automated processes to repeatedly execute a set of actions on multiple items until a defined condition is met, mimicking real-life repetitive tasks.

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so let's learn about looping workflows

otherwise known as recursive workflows

so as I mentioned in the previous

session about back-end workloads one of

the really cool things about them is

that they can trigger themselves so you

can have one that does an action and

then at the end of the workflow decides

it's going to start itself again and

just keeps going round and round and

round like that so doing that is called

a recursive workflow or a looping

workflow because it is effectively

making a loop that goes round and round

and that is really useful if you want to

make changes to a lot of different

things so although the whole looping

concept can seem like it's something

straight out of computer programming

which it is actually in real life you

use it all the time when you're doing

things that require a lot of repetitive

tasks so say for example you have a pile

of 50 Christmas cards that you need to

write and sign you might have a pile of

them on the left hand side of your desk

you take the first one off the top you

write it you sign it you put it in an

envelope and you put it on the right

hand side of your desk and then you go

over and you take the next one and you

do the same and each time you're taking

a card you are running a process you're

doing the same thing which is write the

card sign it put it in the envelope and

then put it on the right hand side of

the desk and you keep repeating that

process until you get to the end of the

pile and then when you've got the last

one done from the left hand pile and

you've got a nice pile on the right hand

side then you stop so looping or

recursive workflows working exactly the

same way they take a list or a pile of

things that need to be done they run the

same process on each one one by one

until they have run out of things to run

the process on and then they stop so

it's exactly the same principle and

really works very similarly to how you

would do it in real life so let's take

this example here I have 10 things in my

database which I want to make changes to

okay and if you want you can imagine

that these are Christmas cards or just

anything users tasks projects whatever

okay so the first thing that bubble will

do when you said I want to make a change

to a list of these things is that it

will number each thing in the list okay

it won't explicitly say it's doing this

but each item will have a number that

you can refer to so it won't just be a

kind of jumbled list of things it will

be a list that's in an order

then you will tell bubble the process

that you want to run on these things so

it could be I want to update one field

it could be I want to update 20 Fields

it could be I want to delete them or I

want to save them onto something else uh

it could be any one of a number of things

then bubble will take the first item in

the list or rather you will instruct

bubble start with the first item in the

list the item numbered one and run that process

process

then once you've done that we will tell

bubble to make a decision whether to

continue or whether to stop there so if

the answer is the question should I

continue is no then bubble will stop

if the answer is yes then bubble will go

back to the list but this time it won't

take item number one

we will tell it to take item number two

and then item number three and four and

so on and each time it'll go through the

process then it will ask the question

should I continue yes or no and if the

answer to that question is yes then it

will keep going through each item one at

a time

until it gets to the end

and the last item number 10 I'll go

through the process and then it will get

to the question should I continue and

this time

the answer will be no

and so it will stop the process and the

looping will have been done and all of

these items will have been updated so

just like the question here where you'll

say well have I run out of cards to fill

in when the answer is yes which means I

should stop then you will stop signing

cards in the same way bubble will do the

same so how does it know how does it how

do we formulate this question so that it

knows when to keep going and when to

stop well all we do is that while we are

sending through this Loop we are also

sending through two other pieces of

information one of those a piece of

information is the total number of

things so we know there are 10 things in

this list so we tell but well there are

10 things in the list and then we also

tell it what is the number of the

current thing you're working on so one

two three four five six seven eight nine

or ten so anytime it is number one to

nine we will allow it we will say okay

you can continue as long as the the

current thing you're working on is not

item number 10 in

when the current thing you're working on

is item number 10 that is the last thing

in the list and therefore once you've

done the process you should stop

so although this might seem quite

abstract this is almost exactly how

looping workflows work and I will show

you now in some real examples so on this

page we have a imaginary project and we

have a button here to create tasks and

we have a button here to update tasks so

the first one I want to show you how you

can use a recursive workflow to create a

number of things in in the database and

then we're going to see how you can

update them so all I've done is I've

made a little interface here where you

can specify the number of tasks that you

want to create and then press create but

I haven't done any of the workflows yet

because we are going to do that together so

first let's go to our backend workplace

and we're going to make a new API

workflow which is going to be create tasks

tasks

and we are going to untick that and now

we're going to Define some parameters

some information that we want to send

through to this backend workflow so the

first thing is going to be

total tasks which is going to be a

number so this is going to be the total

number of tasks that we want created and

it's going to be that number that we

type into the box before we press create

then we're going to have something

that's called current task so that

is also a number and that is just the

number of the tasks that is currently

working on and we're going to change

that number each time it Loops through

so that goes through every task and the

third thing is going to be project

because each of these tasks is going to

be attached to a certain project the

project that we've we made up on the

page because we want to be able to see

all the tasks associated with that

project so these are all the parameters

that we need now we're going to close

that and we are going to create

a new thing and the type of thing we're

going to create is a task

and the fields we're going to set so

we're going to set project equals

and it's going to be one of our

parameters project so it's being passed

through from the page when we trigger

this workflow and then we're going to

let's set the name equals task

task

and then

let's put in a dynamic number so let's

put in the current task number so it's

going to say task and then when it's the

first task it'll be one or the second

task will be two and so on so it's going

to be name equals task and then a number

and that's all the fields we want to set

then we are going to schedule

this workflow to run again because the

first time it goes through it's going to

do it on the first task but we wanted to

do a number of tasks that we are going

to specify so we're going to to schedule

itself at the current date and time

and we're going to tell it total tasks

that's going to remain constant so if we

say we want 20 tasks that number will

remain the same we still want 20 tasks

but the current task is going to be

plus one so this is this is a really

important part because this means that

the next time it runs

this API workload this back-end workflow

that current task number has gone up by

one so the current task is going to be

called task

two for example if the first one was one

and then three and so on

and then the project that is going to

remain the same so the only thing that's

going to change and this is uh pretty

much the same with most recursive

workflows is that the there is a number

that changes each time so that it knows

that it's working through these tasks

and then very importantly we want this

workflow to stop at a certain point

because if we just trigger this workflow

now it's just going to keep going and

going and going and we haven't actually

told it to stop when it reaches the

number of total tasks so it's just going

to keep going and going going it's not

even paying any attention to this number

at all and it will be effectively in an

infinite Loop which is just going to

quickly fill up your database and cost

you loads of workload units so we

definitely need to make sure this stops

and the way we do that this is the

question where we where it asks should I

continue or not so this is where we

specify that as in this only when here

so when it's scheduling itself we're

going to put in a condition here so we

only want it to run again when the total

number of tasks

so that's a for example 20 is bigger than

than

the current task number

so if you imagine total number of task

is 20

. so when current task is one it's going

to get to this question it's going to

say oh 20 is bigger than one so I'm

going to I'm going to run I'm going to

schedule this then when it gets to 19

it's still going to say 20 is bigger

than 19 so that's okay but as it

schedules itself again it will add 1 to

19 and it will get 20. so the next time

it round it goes create tasks create a

new task task 20 it will get to here and

it'll say total tasks

is 20. current task is 20. so total

tasks is equal to current task is not

bigger than current task therefore I

should stop therefore I should not schedule

schedule

myself again so at that point it will

stop having created 20 tasks in the

database so this bit here this

conditional is what prevents it from

running infinitely and this is where it

asks the question should I continue in

the same way as if you're preparing your

Christmas cards you would look to see if

there are any left in the pile and if

there are none left in the pile then you

know you've completed your Christmas cards

cards so

going back to our page

so when the button create tasks is

pressed it shows pop-up create and then

when this button

is pressed

we are going to schedule

an API workflow

and it's going to be create tasks and

schedule date is going to be current

date and time

and the total tasks is going to be input

number of tasks value

the current task we always start with one

one

so it's always going to start with the

first one and then the project is going

to be the current page project

so that's going to send through the

number one to start with and then every

time it Loops through that it's going to

go two three four five six seven until

it gets to whatever number we type into

create tasks so let's do 20 tasks and

click create

and I forgot to hide the pop-up as you

can see they are being created in the

back end through this workflow and they

are one by one appearing on the page or

not one by one but

in groups so until we get to 20

and then hopefully it should stop there

because if it doesn't then we've made a mistake

mistake

or I've made a mistake okay so there it

has created all 20 tasks and it has

stopped which is exactly what we wanted

it to be

so the second example is updating tasks

so say we want to update all 20 of those

tasks how would we do that

so let's go to our backend workplace and

let's create a new backend workflow

which we will call update tasks

and again we will untick that and this

time we are going to have one more

parameter which is going to be

the list of tasks because when we did

the create tasks there was no list of

tasks to send it we were asking it to

create the tasks at that time but this

time when we're updating tasks we have

to tell it what tasks do we want it to

update so we are going to send it a list

of tasks so I have to tick this box here

to tell it that it should be expecting a

list here

we're also going to send through a value

for the total tasks which is going to be

a number

now this is optional

um you cannot you can actually uh just

ask it to count how many are in the list

of tasks every time but that just

requires that bubble does this count

every single time it Loops through the

workflow and because this number is not

going to change once once we sent this

list through that number will remain

constant we may as well just count it

once and then send it through as a

number so that's just a preferred way of

doing things we also want to send

through a number that represents the

current task we're working on so in this

workflow we call that current task

more commonly I would call it something

like index or iterator so index is

probably a simpler word but usually I

will always just call it index because

it's just simpler for me to remember so

index is the number of the tasks that we

are currently working on and that's the

number that we're going to increment by

one each time it Loops through so now

we've got those three things the list

the total number and the index then we

can but the first action in which is

going to be make changes to a thing

rather than create things we're making

changes and the thing we want to change

so we are only going to change one of

these tasks at a time the thing we're

going to change is tasks so

it's showing me tasks because this is

one of our parameters the only other

options a current user into a search for

but we want to change the list of tasks

but we can only change one thing at a

time so it says you're trying to change

a list of tasks you probably want to

change the first item of this list okay

so it is correct but we don't want to

say tasks first item because that means

every time it leaps through it's just

going to change the first item we

actually want to change item number

and then it's expecting a number here

and the number we're going to put here

is index because this is the number

that's going to change so the first time

it's going to say tasks list item number

one then the next time it will be the

tasks list item number two and so on so

that's how we are going to iterate

through each of the tasks in the list

changing them one by one and then the

thing we're going to change I think is

we are just going to change the name to task

task

and then I'm going to put in the

index number

and then I'm going to say up updated

updated

okay so task one that will change the

name to task one dash updated and task

two will be task 2 updated okay and that

will just show us that we have updated

those things and then we are going to

for the next step schedule an API

workflow and that workflow is going to

be update tasks and we're going to

schedule it for the current date and

time and the tasks list is going to

remain exactly the same

total tasks is going to remain exactly

the same

and there so we know that number is

going to be 20 in our case so it will be

20 every time but the index is going to be

Plus 1. so each time it's going to add

one to the index until we get to the end

and then very important we need to put

in our conditional to make sure it stops

at the right time so stop so we want it

to continue only when total tasks is

bigger than index and then when it gets

to the point where total tasks is not

bigger than index I.E total task equals

index then it will stop scheduling this

and it will stop doing this update

so now we've done that we can go back to page

page

and we can find the pop-up which is

update and I actually I was planning on

having a kind of dynamic field that we

could type in there and send that

information through but I'm going to

delete that in fact I'm going to delete

this whole pop-up because I think that

slightly over complicates things and in

most cases you won't need to do stuff

like that so update tasks

I'm just going to edit this workflow and

we are going to schedule

an API workflow and that's going to be

update tasks and it's going to be

current date and time

tasks so this is the important bit this

is where we tell it the list of tasks

that we want it to do this thing on so

in our case we are going to say

we could actually say repeating group

tasks list of tasks or we could say do a

tasks where the

the project

project equals

equals

current page project so

that will have the exact same result

because repeating group tasks is that's

how it's getting its list of tasks by

doing this exact search so it doesn't

really matter more commonly probably you

would do a search for tasks like this

but in our case we could have just

referred to the repeating Group total

tasks is going to be if I copy that expression

expression

it's going to be search for tasks count

count

so that will return 20 in our in our

situation and then index is always one

to start with because we want it to

start on number one

uh and it's worth pointing out that in

some situations you may not want it to

make changes to all the tasks in the

database so you can put as many

constraints as you want in here you can

have users selecting a certain number of

tasks or things from a list the list you

Center in here is entirely up to you and

depends on your needs in our case we are

sending through every task that is

linked to the current page project but

you could equally restrict it to only

you know half of those tasks if you only

want to update half of them

so once we have filled this in

um that's all we need to do

so you can see how it's going through

looping over and over and updating all

of them just to change the name like that

that

and then it has hopefully stopped at the

end and I'm pretty sure it has you can

see the kind of length of time that it

takes to do it and the way it can leap

through which is just a really handy

thing to do so

um I often use Loops like this to fix

data in my database so often when I've

got an app that I've been developing for

quite a while I'll realize that I want

to make a change to the database I want

to add a new field onto users for

example so for example say I had an app

that was completely free and then I

decided that I wanted to make it a paid

app then I might want to leap through

all the users in the database and you

know give them a free trial end period

or give them a flag that said a free

user or a flag that says like you know

Legacy user so anytime where I want to

make changes to all the things in the

database I use recursive workflows like

this to leap through likewise I have

apps where I need to once a day I want

to Loop through every user in the

database and say update a value on their

on their user or update a figure on

their dashboard and do calculations and

stuff so I will have a workflow that

once a day will schedule a recursive

workflow to Loop through every user or

every project or everything and update a

field on it so that the next time the

user logs in they will see this figure

has been updated so recursive workflows

are really really useful for that kind

of thing for doing updates to large

amounts of data there is also an option

to make changes to things on a list

which I'm going to do a session on next

but in general recursive workflows are a

better way of doing things because you

can have absolute visibility over

what is being updated and when so for

example we could have in our back-end

workflows we could have

in this workflow had

an email

which sent

to well

to whoever

that said update complete and we could

it only sends that email when

total tasks is index so we know that

this will only run at the point where

this is no longer true when it gets to

task 20 in our case then this will not

run and this will run so on the final

time it'll run and it'll send us an

email saying update complete and then we

know that that update has been done so

if you've got an update that takes an

hour to run because you've got thousands

of things in your database then it could

be really useful to receive that email

to know that it has completed so

recursive workflows are very useful in

that sense and we could also have it so

that once this is completed we could

schedule another recursive workflow to

do other things and because we are able

to tell when this is completed we will

then know when we can schedule this

other workflow to start and so on so you

can daisy chain a load of workflows

together uh all waiting until the formal

one has completed whereas if you use the

other action which is a schedule an API

workflow on a list you have no way of

knowing when that has finished so it's

definitely not as easy to control and

easy to manage as a recursive workflow

on the flip side now that bubble has a

workload units as part of its pricing

um it's definitely worth being very

careful when you're making your

recursive workflows because if you had

one for example that turned out to be an

infinite Loop because you'd forgotten to

put this in there uh and you and you

failed to stop it from running

um then you could be in trouble because

it's effectively going to use an

infinite amount of workload units now

bubble has said they're not going to

penalize people who have made a by

mistake made an infinite Loop and used

uploads of workload units by that so I

don't think you really need to be

worried about that but in general you

might find that your app has some

recursive workflows which are really

degrading the efficiency of the app so

you just have to be a bit careful about

when you're using this recursive

functionality and the last thing that's

worth pointing out is if you do make an

infinite Loop you can always if you go

into your logs and go to your scheduler

and click show

so there's nothing here now but this

will show you all this all the workflows

that are scheduled after a current time

so this is current date and time but you

can put this at any time in the future

and it will show them and you can click

cancel or you can click cancel all or

you can pause them so if you do have an

infinite Loop running you do have a way

to cancel them to cancel it or to stop

it from running so just be aware of that

especially while you're learning because

you may well set off an infinite Loop

but don't be too worried because you

have this way of stopping it here so

that concludes the session on recursive

workflows I hope it has been interesting

these are definitely something that you

are going to need to use at some point

so worth learning I know that the the

whole thing about that the index and the

total can be a bit confusing but once

you practice with them a few times

you'll get the hang of it and it'll

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