防止Laravel将多个记录添加到数据透视表中 [英] Preventing Laravel adding multiple records to a pivot table

问题描述

我有多对多的关系设置和工作，添加一个项目到我使用的购物车：

I have a many to many relationship set up and working, to add an item to the cart I use:

$cart->items()->attach($item);

哪些添加一个项目到数据透视表（应该），但如果用户点击再次链接以添加已添加的项目，它会在数据透视表中创建一个重复条目。

Which adds an item to the pivot table (as it should), but if the user clicks on the link again to add an item they have already added it creates a duplicate entry in the pivot table.

是否有内置方式将记录添加到数据透视表中如果还不存在？

Is there a built in way to add a record to a pivot table only if one does not already exist?

如果没有，我如何检查数据透视表以查找匹配的记录是否已经存在？

If not, how can I check the pivot table to find if a matching record already exists?

推荐答案

您可以通过编写一个非常简单的条件来检查现有记录的存在：

You can check the presence of an existing record by writing a very simple condition like this one :

if (! $cart->items->contains($newItem->id)) {
    $cart->items()->save($newItem);
}

或者你可以在数据库中添加unicity条件，它会抛出尝试保存双精度的例外。

Or/and you can add unicity condition in your database, it would throw an exception during an attempt of saving a doublet.

您还应该看看下面Barryvdh更简单的答案。

You should also take a look at the more straightforward answer from Barryvdh just below.

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