Rails：将关联的一部分推入数组的优雅方法

Question

I've got a post and an author model.

author has_many :posts

Now I have an author with several posts

Is there an elegant way to get only the posts' titles as an array, not the whole post object?

So, not just author.posts but something like author.posts.only(:title) to get an array of titles. Eg ['post1','post2','post3'] .

That .only(:title) syntax is from the JSON module and doesn't work in this case but there might be something more elegant than iterating over the posts and pushing the titles into a new array. Something that queries the DB like select titles from posts where author_id = 23 .

?

Answer 1

Use pluck

author.posts.pluck(:title)

http://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck

pluck(column_name)

This method is designed to perform select by a single column as direct SQL query Returns Array with values of the specified column name The values has same data type as column.