在 Rails 模型/表中验证存在与 null false [英] Validates presense vs null false in Rails models/tables

问题描述

我在玩 Rails 管理员，我注意到了一些事情.

I was playing around with Rails admin and I noticed something.

在模型中定义如下的属性，在Rails admin中算作必需"

Attributes which are defined as below in model, counted as "Required" in Rails admin

 validates :user, presence: true

但是，下表中定义的属性(架构/迁移)仍被视为可选"

However, attributes which are defined as below in table (schema/migration) still counted as "Optional"

t.datetime "created_at",:null => false

我会假设这两个是相同的，除了验证错误弹出的级别.我错了还是这是 Rails 管理员错误?这两者是否都确保成功保存该字段是必需的，还是有区别?

I would have assumed that both of these are identical except perhaps the level from which the validation error pops up. Am I wrong or is this a Rails admin error? Are both of these ensuring that this field will be required for a successful field save or is there a difference?

推荐答案

添加 :null =>false 表示这是数据库限制，即在任何情况下数据库都不允许空值.

Adding a :null => false means that this is a database restriction, i.e. under no circumstance will the database allow a null value.

添加 presence: true 是模型级验证，因此将在对象插入数据库之前进行.在某些情况下您可能想要破坏这些验证(例如边缘情况或在您的规范中)您可以使用 :validates => 跳过验证.false 并且对象仍然会进入数据库，如果有空数据库限制，这不会发生.

Adding a presence: true is a model level validation so will take place before the object is inserted into the database. There may be a case you want to break these validations (for example edge cases or in your specs) You can then skip validation using :validates => false and the object will still go into the database, with a null DB restriction, this won't happen.

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