How to Handle Non-Existent Rows in GORM\'s Delete Function?

Handling Errors in GORM's Delete Function

When working with database deletions using GORM, it's crucial to consider how you want to handle non-existent rows. By default, GORM does not throw an error when trying to delete a non-existent row. Instead, the result.Error field remains nil.

To alter this behavior and return an error for non-existent rows, you need to inspect the RowsAffected field. Here's how you can modify your DeleteCategory function:

<code class="go">func DeleteCategory(id uint) error {
    c := Category{ID: id}

    db := db.Delete(&c)
    if db.Error != nil {
        return db.Error
    } else if db.RowsAffected < 1 {
        return fmt.Errorf("row with id=%d cannot be deleted because it doesn't exist", id)
    }

    return nil
}</code>

In this modified function:

1. GORM's Delete method is invoked, assigning the result to db.
2. If db.Error is not nil, an error is returned.
3. After confirming that there is no general error, db.RowsAffected is checked. If it is less than 1, indicating that no rows were affected by the delete operation, a custom error message is returned.
4. A nil error value is returned if the row deletion was successful.

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