[英]Ruby Conditional argument to method
I have some 'generic' methods that extract data based on css selectors that usually are the same in many websites. 我有一些基于CSS选择器的数据提取方法,这些方法通常在许多网站中都是相同的。 However I have another method that accept as argument the css selector for a given website.
但是,我有另一种方法可以接受给定网站的CSS选择器作为参数。
I need to call the get_title method if title_selector argument is nos passed. 如果未传递title_selector参数,则需要调用get_title方法。 How can I do that?
我怎样才能做到这一点?
def scrape(urls, item_selector, title_selector, price_selector, image_selector)
collection = []
urls.each do |url|
doc = Nokogiri::HTML(open(url).read) # Opens URL
@items = doc.css(item_selector)[0..1].map {|item| item['href']} # Sets items
@items.each do |item| # Donwload each link and parse
page = Nokogiri::HTML(open(item).read)
collection << {
:title => page.css(title_selector).text, # I guess I need conditional here
:price => page.css(price_selector).text
}
end
@collection = collection
end
end
def get_title(doc)
if doc.at_css("meta[property='og:title']")
title = doc.css("meta[property='og:title']")
else doc.css('title')
title = doc.at_css('title').text
end
end
Use an or
operator inside your page.css
call. 在
page.css
调用中使用or
运算符。 It will call get_title
if title_selector
is falsey (nil). 如果
title_selector
为false(nil),它将调用get_title
。
:title => page.css(title_selector || get_title(doc)).text,
I'm not sure what doc
should actually be in this context, though. 不过,我不确定在这种情况下实际应该使用什么
doc
。
EDIT 编辑
Given your comment below, I think you can just refactor get_title
to handle all of the logic. 鉴于您在下面的评论,我认为您只需重构
get_title
即可处理所有逻辑。 Allow get_title
to take an optional title_selector
parameter and add this line to the top of your method: 允许
get_title
使用可选的title_selector
参数,并将此行添加到方法的顶部:
return doc.css(title_selector).text if title_selector
Then, my original line becomes: 然后,我的原始行变为:
:title => get_title(page, title_selector)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.