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[Music] hey guys in today's video what I'll be talking about is doing some custom validation on fields in your forms in Jango so there are many ways to do this but I'm going to assume that you're doing this validation only once in a particular form if you're doing it in multiple places like your cost multiple forms then you may want to consider making your own validator or even your own field but since we're limited to one form there's a particular method that you can use to validate things in one form only so what I have already is a very simple form setup with the text input and a submit button and then if we look here we have a form called anagram form with one value we have a template that renders it and we have views that handle the anagram form so nothing here is really important it's just to get the form to display and the template is very straightforward so what I'll be doing is working on the anagram form here so what I want to do is I want to check and see if this test value that is passed in is an anagram of something so what I need to do first is write a simple function to determine if this is an anagram or not so I'll do that now and without deleting so I'll call this is anagram and it'll take in two values and it will return the comparison between both of them after they've been sorted so if they are the same after being sorted then you know they're an anagram of each other so now what I want to do is create the custom validation so to do that I'm going to create a method in my anagram form and it's going to have a certain type of name so it starts with clean and then followed by the field name that has the custom validation so clean and then the field is test value and since this is a method it takes himself and what I'll do in this method is I will raise an error if the validation phil's and i will return the clean data if it succeeds so let me start by getting the data so data equals self clean data gets test value and then I'll return this so return data so this is pretty simple this is just like using the clean data dictionary when you're in views but instead we're in the form so we have to use self and I'm just getting the value after has been clean the first time and then what I'm going to do is I'll perform some kind of validation here so I want to use this is anagram function that I have up here and to do that I'll say if not so if it is an anagram I wanted to just return normally so if it's not an anagram so if not is anagram I'll pass them the data is the first value in the second value let's say listen so if it's a anagram of the word listen then it will pass if it's not then it's going to fill so here if it fills inside the if not then I just raise a validation error from forms so raised and then form stop validation here so Django is going to catch this validation error and inject the message that I put here into the form errors object and then we can actually see that on the front end so I'll say this is not an anagram of listened and now let's try so refresh now just put in some nonce it's and make sure that it works so now I see this is not an anagram of listen so if I do put an anagram of listen let's say silence it passes and if I click it again if I add another T is no longer an anagram if I remove of T it's not an anagram but if I put that T back then everything passes so we know the custom validation is working so this method will get called automatically by Django once the form is being validated which is this is valid function here is valid method on the form object here so now let's say we want to do some validation multiple fields at the same time so I have one field here but let's say I have a form with two fields the second field will allow me to take in a second string and then I can say if the two values that are passed and by the user are anagrams or not so I'll just comment out this one because it's gonna interfere with the one that uses both and I'll create another field it's gonna be pretty much the same format as this is just going to have a different name so let's say value no not value test anagram there we go so forms char field and then label and I don't know why this is your name let's just make this test value label is going to be test anagram max length can be a hundred again and then the widget this is just so ball moe works so forums text input and then we're going to assign input here and I'll move this closing one here okay so now let me just modify my form a little bit so I get this second field in and let's see so we have a control here and it's going to take inform test anagram and I'll leave the error message on the first field just for simplicity purposes so let's see if this has two fields now or if something broke something broke so in my form I forgot the equal sign okay so let's try that again okay so I have two fields now so if I put text in both nothing happens because I no longer have that custom validation I removed it but now I want to compare if they are anagrams of each other so to do that I can no longer use clean and then test value because I'm going to be comparing two things so anytime you want to compare two or more fields to each other in your form you want to use just clean so the first thing about clean is you need to get the clean data from the first run of clean so this is your own implementation of clean but the form itself has its own clean method so that one actually needs to run first and then you can do your validation after that so first you get the clean data from the first run of clean so to do that you can create a variable called clean data and then you can call the clean data from the forms odd form so super and then clean so it just calls the same method already exists from forms dot form and this one's going to run the typical validation and then it's going to return the clean data so once you have it you can go ahead and actually get the values from it so I have a test value so clean data dot get test value and then I also have the test anagram so clean data get test anagram and then what you want to do is you want to make sure these two values actually exists because in some forms these aren't required so if you're going to validate you want to actually make sure something something's there but of course it depends on your exact use case so if test value and tests anagram then we can go ahead and do something and this is the part where I will check to see if the two are anagrams of each other so I'll have another function here or another if statement here with the is anagram function so if not is anagram and then for X I'll pass and test value for Y test anagram and if it fails then we'll raise the errors so raise forms dot validation error and I'll say these are not anagrams and with this I don't have to return anything because the clean data is already there you can update the data if you want because you have access to it but for this example I'm just going to focus on the validation so I have that here and what I need to change is the error section here so right now I'm just looking for errors in test value but now this air since it's inside of clean instead of a particular fields clean method it won't end up on any field when you look at the air so right here these are looking for errors on test value so what you want to do is you want to look at the errors on the form itself so to do that instead of test value and dot errors you use form non filled ears so this gives you the airs that are about the form in general not about one specific field so now let's try this and then we'll try listen and silence things pass if I remove one character from silent then I see these are not anagrams and of course I can try with any other text like dog god anagrams cat and ATC anagrams but if I change it to a TD these are not anagrams so anything I put here is going to be compared with this other field and that's where the validation comes into play because two fields are being compared to each other and if they aren't anagrams an error gets raised and if they are then everything continues as normal the form gets submitted and then you can handle this in your views however you want to save it to the database do whatever but the validation parts is the important part that I wanted to cover so that's it for this video if you want to learn more about Django I have the understanding Django course on my website so I'll put a link in the description below if you want to go to it if you also want to get a cheat sheet for a Django I have that I'll put a link in the description to that as well it's just a pretty print accom slash Django but I'll put a link and as far as this video is concerned if you have any questions about the video feel free to leave a comment down below if you like this video please give me a thumbs up and if you have subscribed to my channel already please subscribe so thank you for watching and I will talk to you next time