只有當它爲零時，我如何在ActiveRecord對象中設置屬性？

Question

對不起，我覺得我今天有點笨

class Mutant < ActiveRecord::Base 
    attr_accessible :style 

    before_create :setup_values 


    private 

    def setup_values 
    style = "hardcore" unless style 
    end 
end 

我喜歡把這種東西在控制檯像

Mutant.create(:style => "rampage") # expected is Mutant.first.style == "rampage" 
Mutant.create # expected is Mutant.last.style == "hardcore but this doesn't work 

Answer 1

只是覺得在API

def setup_values 
    write_attribute :style, "hardcore" if style.blank? 
end 

tadaa和它的作品:)

Answer 2

1. 首先，看這個問題：What is the best way to set default values in activerecord
2. style = "hardcore" unless style將實例化一個名爲「風格」，而不是設置現有屬性的新變量。將其更改爲參考self像這樣：self.style = "hardcore" unless style
3. 最後將作業寫入self.style，如下所示：self.style ||= "hardcore"這是您當前編寫的快捷方式。

我可能會寫這樣的：

class Mutant < ActiveRecord::Base 
    attr_accessible :style 
    after_initialize :setup_values 

    private 
    def setup_values 
    self.style ||= "hardcore" 
    end 
end