Treat error return in codeigniter

Question

A call to the delete method returns me the following error.

Error Number:

ERROR: update or delete on table "matricula" violates Foreign key Constraint "matricula_matricula_cobranca_fk" on table "movimento_cobranca" DETAIL: Key (matricula)=(1908) is still referenced from table "movimento_cobranca".

DELETE FROM matricula WHERE matricula IN (1908)

Filename: models/Matricula_model.php

Line Number: 166

---

However I need to treat this error and display a message to the user just stating that it did not work.

In the controller I’m just validating the input and calling in the Model.

Controller

public function excluir($matricula) {
   if ($this->matricula_model->excluir($matricula)->dbReturn === true)
     echo json_encode(['codigo' => 0]);
   else
     echo json_encode(['codigo' => 1]);
}

Model

function excluir($matricula)
{
    if ( $lista_matricula != "" ) {
        $sql_exclusao = "DELETE FROM matricula WHERE matricula IN (". $matricula .")";
        if (!$ret = $this->db->query($sql_exclusao))
        {
            return $this->buildReturnObject($this->db->error(),false);
        }
        return $this->buildReturnObject('',$ret);
    }
    return false;
}

---

I know why the error is occurring and I don’t need to treat it at the moment (because it refers to the comic). What I need is a way to return a value to my view (I used booleans, but it could be anyone else) to be able to display an Alert, a message or whatever. I need my return to be true or false to pass to my view a code (0 or 1) and display according to it a message, but the way I did not work.

Answer 1

For handling bank errors you can create a new class CI core with Ci_model extends and create a function to generate an object with the return of success and/or error.

Example of the function in the new Class:

class CustomModel extends CI_Model
{
    public function __construct()
    {
        parent::__construct();
    }

    protected function buildReturnObject($dbError,$dbReturn)
    {
        $retObj = new stdClass();
        $retObj->dbError = $dbError;
        $retObj->dbReturn = $dbReturn;
        return $retObj;
    }
}

And you can create treatments in the function of your Model denying the query (error) in a check IF (will be TRUE if any error occurs in the query), and if it occurs you can return the created object with the occasional error, if it does not occur you return the object with the query successfully return, example of how it would look inside its function in the model:

if (!$ret = $this->db->query($sql, $binds))
{
    return $this->buildReturnObject($this->db->error(),false);
}
return $this->buildReturnObject('',$ret);

So when you receive an unexpected result in the Controller you’ll be there to see what you want to do. Do not forget that in order to use the new function created to manipulate the return object, every Model you create should extend its class CustomModel.

Remember that in Controller, if you use this format, you will always have to reference the position ->dbReturn after the end of the query, if something goes wrong this position will get false, and you can access the error return in ->dbError. The query will always follow this syntax:

$this->classe_model->getXXX($param)->dbReturn;

Answer 2

Use Try Catch to treat exception.

Answer 3

Try the following to see if you succeeded in the model or not:

if(!$sql_exclusao){
    tratamento da excessão...
}

Or something like that. Where $sql_delete will be bool whether or not the query worked. I don’t know if the environment you use allows it, but php has this power to know if the query returned well or not.