Ruby-on-rails 创建或更新 has_one ActiveRecord 关联
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Creating or updating a has_one ActiveRecord association
提问by Still Real
I've been trying to get my head around ActiveRecordassociations but I have hit a bit of a brick wall, and no matter how much I review the ActiveRecorddocumentation, I can't work out how to solve my problem.
我一直在尝试解决ActiveRecord关联问题，但我遇到了一些障碍，无论我查看了多少ActiveRecord文档，我都无法弄清楚如何解决我的问题。
I have two classes:
我有两个班级：
Property -> has_one :contract
Contract -> belongs_to :property
In my contract class, I have a method to create_or_update_from_xml
在我的合同类中，我有一个方法来 create_or_update_from_xml
First I check to make sure the property in question exists.
首先，我检查以确保有问题的财产存在。
property_unique_id = xml_node.css('property_id').text
property = Property.find_by_unique_id(property_unique_id)
next unless property
And this is where I get stuck, I have a hash of attributes for the contract, and what I want to do is something like:
这就是我陷入困境的地方，我有一个合同属性的哈希值，我想做的是：
if property.contract.nil?
# create a new one and populate it with attributes
else
# use the existing one and update it with attributes
I know how I would go about it if it was raw SQL, but I can't get my head around hte ActiveRecord approach.
我知道如果它是原始 SQL，我会怎么做，但是我无法理解 ActiveRecord 方法。
Any hints past this road block would be hugely appreciated.
任何通过此路障的提示将不胜感激。
Thanks in advance.
提前致谢。
回答by Frederick Cheung
if property.contract.nil?
property.create_contract(some_attributes)
else
property.contract.update_attributes(some_attributes)
end
Should do the trick. When you have a has_oneor belongs_toassociation then you get build_fooand create_foomethods (which are like Foo.new and Foo.create). If the association already exists then property.contractis basically just a normal active record object.
应该做的伎俩。当您拥有has_oneorbelongs_to关联时，您将获得build_foo和create_foo方法（类似于 Foo.new 和 Foo.create）。如果关联已经存在，那么property.contract基本上只是一个普通的活动记录对象。
回答by Kinaan Khan Sherwani
Just another way of doing it using ruby OR-Equaltrick
使用 rubyOR-Equal技巧的另一种方法
property.contract ||= property.build_contract
property.contract.update_attributes(some_attributes)
Update:
更新：
@KayWu is right, the above ||= trick will create the contract object in the first line, rather than just building it. An alternative would be
@KayWu 是对的，上面的 ||= 技巧将在第一行创建合约对象，而不仅仅是构建它。另一种选择是
property.build_contract unless property.contract
property.contract.update_attributes(some_attributes)
回答by r-t-t
Property.all.each do |f|
c = Contract.find_or_initialize_by(property_id: f.id)
c.update(some_attributes)
end
I don't know whether this is the best solution, but for me it more succinctly
我不知道这是否是最好的解决方案，但对我来说更简洁
