Simplify Assignment in Ruby on Rails

Question

I just want to assign the value of variable B to variable A only if B is not nil. And I want to simplify the code as possible. So I found the one.

A = B if B

But variable name is long such as data[:Symbol1][:Symbol2]... , anyhow same variable name is duplicated.

Can anybody help me with simplifying this code?

Not completely clear the part of the duplicated name, can you make an example. Try `a = b || a`. — iGian, Mar 05 '20 at 15:17

score 1 · Answer 1 · answered Mar 05 '20 at 15:17

1

You might try the presence method.

Your code would look like

A = B.presence

Example of it in action:

[1] pry(main)> b = nil
=> nil
[2] pry(main)> a = b.presence
=> nil
[3] pry(main)> a
=> nil
[4] pry(main)> b = 'foo'
=> "foo"
[5] pry(main)> a = b.presence
=> "foo"
[6] pry(main)> a
=> "foo"

answered Mar 05 '20 at 15:17

yez

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If `a = :something` you turn a into `nil`. So this is just `a = b`? – iGian Mar 05 '20 at 15:25
In which version of ruby, does it work? b.presence gives error presence undefined in nil:NilClass. – Joe Mar 05 '20 at 15:46
1

@Romeo, `require 'rails'` or `require 'active_support/core_ext/object'`. – iGian Mar 05 '20 at 15:57
@Romeo your title said you were using Ruby on Rails so I gave a Rails specific solution. – yez Mar 06 '20 at 16:03

score 1 · Answer 2 · answered Mar 05 '20 at 21:21

1

I'd say you need A = B || A.

The || operator evaluates and returns the first non-false operand. If B is "truthy", it will return B (and assign it to A). If B is false, A will just be assigned itself.

answered Mar 05 '20 at 21:21

themetar

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2

score 0 · Answer 3 · answered Mar 06 '20 at 04:14

0

2 simple ways:

a = b.presence || a

Or

a = b || a

answered Mar 06 '20 at 04:14

Juan Furattini

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Simplify Assignment in Ruby on Rails

3 Answers3