Query - Call to undefined method CodeIgniter\Database\MySQLi\Connection::where()

I get this error "Call to undefined method CodeIgniter\Database\MySQLi\Connection::where()" when I try this in my model class

PHP Code:

$this->db->table($table);
        $this->db->where($where);
        $this->db->update($save_data); 


however it works fine when

PHP Code:

$this->db->table($table)->where($where)->update($save_data); 


The first approach above worked fine in CI 3. So I suppose in CI 4 I just to have chain or save $db = $this->db;

I get this error "Call to undefined method CodeIgniter\Database\MySQLi\Connection::where()" when I try this in my model class

PHP Code:

$this->db->table($table);
        $this->db->where($where);
        $this->db->update($save_data); 


however it works fine when

PHP Code:

$this->db->table($table)->where($where)->update($save_data); 


The first approach above worked fine in CI 3. So I suppose in CI 4 I just to have chain or save $db = $this->db;

This works like says the documentation:

Model.php

PHP Code:

public function updateData (int $id = 1) {
    $this->db->table($this->table)->where('id', $id)->update(
        [
            'title' => 'New title',
        ]
    );
}

public function anotherUpdateData (int $id = 1) {
    $builder = $this->db->table($this->table);
    $builder->where('id', $id);
    $builder->update(
        [
            'title' => 'New title 2',
        ]
    );
} 


I get this error "Call to undefined method CodeIgniter\Database\MySQLi\Connection::where()" when I try this in my model class

PHP Code:

$this->db->table($table);
        $this->db->where($where);
        $this->db->update($save_data); 


however it works fine when

PHP Code:

$this->db->table($table)->where($where)->update($save_data); 


The first approach above worked fine in CI 3. So I suppose in CI 4 I just to have chain or save $db = $this->db;

This works like says the documentation:

Model.php

PHP Code:

public function updateData (int $id = 1) {
    $this->db->table($this->table)->where('id', $id)->update(
        [
            'title' => 'New title',
        ]
    );
}

public function anotherUpdateData (int $id = 1) {
    $builder = $this->db->table($this->table);
    $builder->where('id', $id);
    $builder->update(
        [
            'title' => 'New title 2',
        ]
    );
} 


In CI-4, you can write more simply.

In conttroler

PHP Code:

$data = [
    'id'=> $id,
    'title' => 'New title 2'
];
(new \App\Models\Post)->save($data); 


In Model

PHP Code:

<?php
namespace App\Models;

class Post extends \CodeIgniter\Model
{  
    protected $table = 'Posts';
    protected $allowedFields = ['title'];

} 


I get this error "Call to undefined method CodeIgniter\Database\MySQLi\Connection::where()" when I try this in my model class

PHP Code:

$this->db->table($table);
        $this->db->where($where);
        $this->db->update($save_data); 


however it works fine when

PHP Code:

$this->db->table($table)->where($where)->update($save_data); 


The first approach above worked fine in CI 3. So I suppose in CI 4 I just to have chain or save $db = $this->db;

A great explanation of Lonnie about this question.

Yes that makes sense! Thx