Sorting a Ruby Array of Objects by an Attribute That Could Be Nil

sorting a ruby array of objects by an attribute that could be nil

How about in Child defining <=> to be based on category.position if category exists, and sorting items without a category as always greater than those with a category?

class Child
  # Not strictly necessary, but will define other comparisons based on <=>
  include Comparable   
  def <=> other
    return 0 if !category && !other.category
    return 1 if !category
    return -1 if !other.category
    category.position <=> other.category.position
  end
end

Then in Parent you can just call children.sort.

Sorting an array based on an attribute that may be nil in some elements

starred.sort_by { |a| [a ? 1 : 0, a] }

When it has to compare two elements, it compares an arrays. When Ruby compares arrays (calls === method), it compares 1st element, and goes to the 2nd elements only if the 1st are equal. ? 1 : 0 garantees, that we'll have Fixnum as 1st element, so it should be no error.

If you do ? 0 : 1, nil will appear at the end of array instead of begining.

Here is an example:

irb> [2, 5, 1, nil, 7, 3, nil, nil, 4, 6].sort_by { |i| [i ? 1 : 0, i] }
=> [nil, nil, nil, 1, 2, 3, 4, 5, 6, 7]

irb> [2, 5, 1, nil, 7, 3, nil, nil, 4, 6].sort_by { |i| [i ? 0 : 1, i] }
=> [1, 2, 3, 4, 5, 6, 7, nil, nil, nil]

Sort array by object properties but with nil? condition in Ruby

First, you probably want to do this sorting in your controller, or even in your model. Putting it in your view makes it a bit noisy.

Second, this solution should work for you. It's fairly short.

@users.sort_by { |u| u.startup.nil? || u.startup.blank? ? 255.chr : u.startup[0].name }

Using 255.chr will push all empty ([]) and null (nil) arrays to the back of the array, as you specified in your comment that you'd like to do that. I assume that there's a cleaner way of representing 255.chr, but I haven't been able to find one.

If a user with no startups is represented as an empty array ([]), then you can remove u.startup.nil? || from that line of code. Similarly, if a user with no startups is represented as nil, then you can remove || u.startup.blank? from it. The code as is assumes that a user with no startups can either have an empty or null array.

Sort an array of hashes when some objects have nil attributes

Treat the nil objects as something else, perhaps 0 or Float::INFINITY?

search_results.sort_by { |user| user.age || 0 }

Since nil.to_i == 0, you could also do:

search_results.sort_by { |user| user.age.to_i }

How to use sort_by with values that could be nil?

Use this syntax,

starred.sort_by { |a| [a ? 1 : 0, a] }

When it has to compare two elements, it compares an arrays. When Ruby compares arrays (calls === method), it compares 1st element, and goes to the 2nd elements only if the 1st are equal. ? 1 : 0 guarantees, that we'll have Fixnum as 1st element, so it should be no error.

If you do ? 0 : 1, nil will appear at the end of array instead of beginning.
Here is an example:

irb> [2, 5, 1, nil, 7, 3, nil, nil, 4, 6].sort_by { |i| [i ? 1 : 0, i] }
=> [nil, nil, nil, 1, 2, 3, 4, 5, 6, 7]

Source.

sorting an array of objects by attribute in ruby raises undefined method error

You need some whitespaces. Any token starting with a : is a symbol in Ruby.

ar.sort! {|i1,i2| (i2.y ? i2.y : i2.x) <=> (i1.y ? i1.y : i1.x)}

And the last line, puts ar is ok.

Ruby: Sort array of objects after an array of name properties

You can use Enumerable#sort_by

my_array.sort_by {|x| @sizes_sort_order.index(x.name) }

Safe sort with array key

(Note: I don't understand what you mean by "first_name and last_name may be false". That doesn't sound right not me. I'm going to assume that they're potentially nil, but not false.)

For a quick and simple workaround, you can coerce the nil values into Strings, for example with:

array.sort_by do |item|
  if item.expression
    [String(item.title), String(item.description)]
  else
    [String(item.first_name), String(item.last_name)]
  end
end

This is almost equivalent to saying "sort alphabetically; nils last".

It does not distinguish between a value being "" vs a nil. If you want to make that aspect of the sorting stricter, you'll need to write something more custom, using the <=> operator.

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