Check if data exists before posting into the database in yii2 - php

Question

I am trying to check if a book is already in the db to avoid duplication. The code below is popping up for both existing and the one not in the database.
public function actionCreate($book_id = 'book_id')
{
$checkmodel = Books::find()->where(['book_id' => $book_id])->one();
if ($checkmodel) {
Yii::$app->session->setFlash('error', 'The book has been borrowed, Please look for another one.');
return $this->redirect(Yii::$app->request->referrer);
}
$model = new Books();
if ($model->load(Yii::$app->request->post()) && $checkmodel->save()) {
Yii::$app->session->setFlash('Success','You have successfully borrowed the book');
return $this->redirect(['view' => 'book_id', $model->book_id]);
}
return $this->render('create', [
'model' => $model,
]);
}

Answer 1

You could avoid the check adding a proper validation rule in you model
anyway for your code you shou,d try checking for not null $checkmodel
if (!is_null($checkmodel) {
Yii::$app->session->setFlash('error', 'The book has been borrowed, Please look for another one.');
return $this->redirect(Yii::$app->request->referrer);
}
https://www.yiiframework.com/doc/api/2.0/yii-validators-uniquevalidator
https://www.yiiframework.com/doc/guide/2.0/en/input-validation

Answer 2

public function actionCreate($book_id = 'book_id')
{
$model = new Books();
// check if post request
if ( $model->load(Yii::$app->request->post()) ) {
// check if book_id exists in table
if ( ! Books::find()->where(['book_id' => $book_id])->one() ) {
// save new record to model
if ( ! $model->save() ) {
// set error message and redirect to 'create' page
Yii::$app->session->setFlash('Error','There was some error in processing your request');
return $this->redirect(Yii::$app->request->referrer);
}
// if model is saved successfully, redirect to 'view' page
Yii::$app->session->setFlash('Success','You have successfully borrowed the book');
return $this->redirect(['view', 'book_id' => $model->book_id]);
} else {
// if book_id exist in table, show error message
Yii::$app->session->setFlash('error', 'The book has been borrowed, Please look for another one.');
return $this->redirect(Yii::$app->request->referrer);
}
}
return $this->render('create', [
'model' => $model,
]);
}
It's always better to check "false" condition in if statements than true. Helps us write cleaner code.
Also there was a syntax error in your redirect to view statement