validations in laravel livewire

@migsAV I changed it and I got another new error

BadMethodCallException Method App\Http\Livewire\PostProjects::file does not exist

If my validation doesn't match with the names of the input or in the table how will it submit anything?

@Snapey I got another error while submitting the form

Property[$cat_id] not found on component: [post-projects]

I tried to replace

public function updatedCategory($cat_id)
    {
        $this->subcategories = Subcategory::where('cat_id', $cat_id)->get();
    }

to this also

public $selectedCategory = null;
public $selectedSubcategory = null;
public $subcategories = null;

public function updatedSelectedCategory($selectedCategory)
    {
        $this->subcategories = Subcategory::where('cat_id', $selectedCategory )->get();
    }

but still not working

@niyo

public function updatedCategory()
    {
        $this->subcategories = Subcategory::where('cat_id', $this->cat_id)->get();
    }

@migsAV I removed it and it's flowing another error

Undefined variable cat_id

@niyo you do not have a public property called category, therefore this is not being called

public function updatedCategory()
    {       
    }

Livewire Lifecycle Hooks

Try and be consistent with your naming conventions

@migsAV I tried it but it still gives me the same error

Undefined variable category

and if I add it again as an argument it push the same error

Property[$cat_id] not found on component: [post-projects]

and I ask myself where $cat_id is from even though it's not included in the codes

class PostProjects extends Component
{
    use WithFileUploads;

    public $category = ' ';
    public $selectedSubcategory = null;
    public $subcategories = null;

    public $title;
    public $image;
    public $price;
    public $description;
    public $qt_title;
    public $qt_answer;

    public $totalTabs = 2;
    public $currentTab = 1;

    public function mount()
    {
        $this->currentTab = 1;
    }

    public function render()
    {
        return view('livewire.post-projects', [
            'categories' => Category::all(),
        ]);
    }

    public function updatedcategory($category)
    {
        $this->subcategories = Subcategory::where('cat_id', $category)->get();
        
    }

    public function increaseStep ()
    {
        $this->resetErrorBag();
        $this->validateData();
        $this->currentTab++;
        if ($this->currentTab > $this->totalTabs) {
            $this->currentTab = $this->totalTabs;
        }
    }

    public function decreaseStep ()
    {
        $this->resetErrorBag();
        $this->currentTab--;
        if ($this->currentTab < 1) {
            $this->currentTab = 1;
        }
    }

    public function validateData ()
    {
        if ($this->currentTab == 1) {
            $this->validate([
                'title' => 'required|min:3',
                'image' => 'required|file|mimes:png,jpg,pdf|max:5120',
                'price' => 'required|min:5',
                'category' => 'required|string',
                'selectedSubcategory' => 'required|string',
            ]);
        }
        elseif ($this->currentTab == 2) {
            $this->validate([
                'description' => 'required|min:10',
                'qt_title' => 'required|min:3',
                'qt_answer' => 'required|min:10',
            ]);
        }

    }

    public function PostProjects () {
        // $upload = $this->file('slug');
        //$path = $upload->store('public/storage/ProjectsPosted');
        $path = $this->image->store('public/storage/ProjectsPosted');

        PostProject::create([
            'title' => $this->title,
            'slug' => $path,
            'price' => $this->price,
            'cat_id' => $this->cat_id,
            'subcat_id' => $this->subcat_id,
            'description' => $this->description,
            'qt_title' => $this->qt_title,
            'qt_answer' => $this->qt_answer,
            'user_id' => Auth::user()->id
        ]);
        $this->reset();
        $this->currentTab = 1;
    }
}

I am using everything you and @snapey 's methods

@niyo I replicated your error and may have fixed it.

Try this code

<?php

namespace App\Http\Livewire;

use App\Models\Category;
use App\Models\PostProject;
use App\Models\Subcategory;
use Illuminate\Support\Facades\Auth;
use Livewire\Component;
use Livewire\WithFileUploads;

class PostProjects extends Component
{
    use WithFileUploads;

    public $category = null;
    public $subcategory = null;
    public $listSubcategories = null;

    public $title;
    public $slug;
    public $price;
    public $description;
    public $qt_title;
    public $qt_answer;

    public $totalTabs = 2;
    public $currentTab = 1;

    public function mount()
    {
        $this->currentTab = 1;
    }

    public function updatedCategory()
    {
        $this->listSubcategories = Subcategory::where('category_id', $this->category)->get();
    }

    public function increaseStep ()
    {
        $this->resetErrorBag();
        $this->validateData();
        $this->currentTab++;
        if ($this->currentTab > $this->totalTabs) {
            $this->currentTab = $this->totalTabs;
        }
    }

    public function decreaseStep ()
    {
        $this->resetErrorBag();
        $this->currentTab--;
        if ($this->currentTab < 1) {
            $this->currentTab = 1;
        }
    }

    public function validateData ()
    {
        if ($this->currentTab == 1) {
            $this->validate([
                'title' => 'required|min:3',
                'slug' => 'required|file|max:5120',
                'price' => 'required|min:5',
                'category' => 'required|string',
                'subcategory' => 'required|string',
            ]);
        }
        elseif ($this->currentTab == 2) {
            $this->validate([
                'description' => 'required|min:10',
                'qt_title' => 'required|min:3',
                'qt_answer' => 'required|min:10',
            ]);
        }

    }

    public function PostProjects () {
//        $upload = $this->file('slug');
        $path = $this->slug->store('public/storage/ProjectsPosted');

        PostProject::create([
            'title' => $this->title,
            'slug' => $path,
            'price' => $this->price,
            'cat_id' => $this->category,
            'subcat_id' => $this->subcategory,
            'description' => $this->description,
            'qt_title' => $this->qt_title,
            'qt_answer' => $this->qt_answer,
            'user_id' => Auth::user()->id
        ]);
        $this->reset();
        $this->currentTab = 1;
    }


    public function render()
    {
        return view('livewire.post-projects',  [
            'categories' => Category::all(),
        ]);
    }
}

You will notice I renamed subcategories to listSubcategories

<div>
    <form wire:submit.prevent="PostProjects">
        @csrf
        @if ($currentTab == 1)
            <div class="tab-1">
                <div class="form-group">
                    <label>Project Title</label>
                    <input type="text" name="title" wire:model="title" class="form-control @error('title') is-invalid @enderror" placeholder="" value="" required autocomplete="title" autofocus>

                    @error('title')
                    <span class="invalid-feedback" role="alert">
                        <strong>{{ $message }}</strong>
                    </span>
                    @enderror
                </div>
                <div class="">
                    <label>Attach files</label>
                    <div class="file-drop-area">
                        <span class="btn btn-outline-info">Choose files</span>
                        <span class="file-msg js-set-number"> or drag and drop files here</span>
                        <input class="file-input @error('slug') is-invalid @enderror" wire:model="slug" type="file">

                        @error('slug')
                        <span class="invalid-feedback" role="alert">
                        <strong>{{ $message }}</strong>
                    </span>
                        @enderror
                    </div>
                </div>
                <div class="form-group">
                    <label>Price</label>
                    <div class="">
                        <input id="price" type="number" wire:model="price" class="form-control @error('price') is-invalid @enderror" name="price" placeholder="Price..." value="" required autocomplete="price" autofocus>

                        @error('price')
                        <span class="invalid-feedback" role="alert">
                            <strong>{{ $message }}</strong>
                        </span>
                        @enderror
                    </div>
                </div>
                <div class="row">
                    <div class="col-md-6 pr-1">
                        <div class="form-group">
                            <label>Choose a Category:</label>
                            <select id="category" name="category" wire:model="category" class="form-control @error('category') is-invalid @enderror">
                                <option value="select">Select Category</option>
                                @foreach($categories as $category)
                                    <option value="{{ $category->id }}">{{ $category->name }}</option>
                                @endforeach
                            </select>
                            @error('category')
                            <span class="invalid-feedback" role="alert">
                            <strong>{{ $message }}</strong>
                        </span>
                            @enderror
                        </div>
                    </div>
                    <div class="col-md-6 pl-1">
                        <div class="form-group">
                            <label>Choose a Sub-Category:</label>
                            <div class="content">
                                <div id="select" class="data">
                                    <select class="form-control" disabled>
                                        <option value="">Select subcategory</option>
                                    </select>
                                </div>
                                <div>
                                    @if(!is_null($listSubcategories))
                                        <select name="subcategory" wire:model="subcategory" class="form-control @error('subcategory') is-invalid @enderror">
                                            <option value="">Select Sub-Category</option>
                                            @foreach($listSubcategories as $listCategory)
                                                <option value="{{ $listCategory->id }}">{{ $listCategory->name }}</option>
                                            @endforeach
                                        </select>
                                        @error('subcategory')
                                        <span class="invalid-feedback" role="alert">
                                        <strong>{{ $message }}</strong>
                                    </span>
                                        @enderror
                                    @endif
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        @endif

        @if ($currentTab == 2)
            <div class="tab-2">
                <div class="form-group">
                    <label>Describe Project You're Posting</label>
                    <textarea rows="4" name="description" cols="180" wire:model="description" class="form-control @error('description') is-invalid @enderror" placeholder="Here can be your description" required></textarea>

                    @error('description')
                    <span class="invalid-feedback" role="alert">
                    <strong>{{ $message }}</strong>
                </span>
                    @enderror
                </div>
                <br>
                <div class="">
                    <h3>Frequently Asked Questions</h3>
                    <hr>
                    <div class="form-group">
                        <label>Question Title</label>
                        <input type="text" name="qt_title" wire:model="qt_title" class="form-control @error('qt_title') is-invalid @enderror" placeholder="Add a Question:" value="" required autocomplete="qt_title" autofocus>

                        @error('qt_title')
                        <span class="invalid-feedback" role="alert">
                        <strong>{{ $message }}</strong>
                    </span>
                        @enderror
                    </div>
                    <div class="form-group">
                        <label>Add Questions & Answers.</label>
                        <textarea rows="7" cols="85" name="qt_answer" wire:model="qt_answer" class="form-control @error('qt_answer') is-invalid @enderror"  placeholder="Add an Answer: i.e. Yes,I also design 3D Logo" required></textarea>

                        @error('qt_answer')
                        <span class="invalid-feedback" role="alert">
                        <strong>{{ $message }}</strong>
                    </span>
                        @enderror
                    </div>
                </div>
            </div>
        @endif
        <div style="overflow:auto;">
            <div class="">
                @if ($currentTab == 1)
                    <button type="button" wire:click="increaseStep()" class="btn btn-success float-right">Next</button>
                @endif

                @if ($currentTab == 2)
                    <button type="button" wire:click="decreaseStep()" class="btn btn-info float-left">Back</button>
                    <button type="submit" class="btn btn-success float-right">Submit</button>
                @endif
            </div>
        </div>
        <!-- Circles which indicates the steps of the form: -->
        <div style="text-align:center;margin-top:40px;">
            <span class="step"></span>
            <span class="step"></span>
        </div>
    </form>

    @if($errors->any())
        {!! implode('', $errors->all('<div>:message</div>')) !!}
    @endif

</div>

@migsAV thanks man It worked, I only had to change this down below to make it work

PostProject::create([
            'title' => $this->title,
            'slug' => $path,
            'price' => $this->price,
            'cat_id' => $this->category,
            'subcat_id' => $this->subcategory,
            'description' => $this->description,
            'qt_title' => $this->qt_title,
            'qt_answer' => $this->qt_answer,
            'user_id' => Auth::user()->id
        ]);

These two guys right here were the ones causing this problem

'cat_id' => $this->cat_id,
'subcat_id' => $this->subcat_id,

man, I don't what to say it's like I owe you a lot, thank you so much

@niyo you're welcome. That's why Laracast is here, to help :) Mark the answer as the best answer so others know it has been resolved.

Happy coding

@niyo use the following

 'price' => 'required|numeric|min:100',

https://laravel.com/docs/9.x/validation#rule-min

@migsAV I am getting the validation right The price must be at least 100.but I want it like The price must be at least $100. Is there a way I can change it

@niyo in the validation you need to add an additional array to customise the error message

$this->validate([
                'title' => 'required|min:3',
                'slug' => 'required|file|max:5120',
               'price' => 'required|numeric|min:100',
                'category' => 'required|string',
                'subcategory' => 'required|string',
            ], [
				'price.min' => 'The price must be at least $100.'
				]);

https://laravel-livewire.com/docs/2.x/input-validation - half way down the page

@migsAV I have another small question for you, I want to make another multi-step-form but this will be submitting on different tables like step1 to table1 and step2 to table2 also step3 to table3 I need to know if it can work the way am thinking or not.

@niyo I'm sure it is possible. I have never done it myself, you might need to play around with it. Maybe look for a thread on Laracast, someone might have asked the same question already.