I am trying to detect if the email address is not one of two domains but I am having some trouble with the ruby syntax. I currently have this:
if ( !email_address.end_with?("#domain1.com") or !email_address.end_with?("#domain2.com"))
#Do Something
end
Is this the right syntax for the conditions?
Rather than an or here, you want a logical && (and) because you are trying to find strings which match neither.
if ( !email_address.end_with?("#domain1.com") && !email_address.end_with?("#domain2.com"))
#Do Something
end
By using or, if either condition is true, the whole condition will still be false.
Note that I am using && instead of and, since it has a higher precedence. Details are well outlined here
From the comments:
You can build an equivalent condition using unless with the logical or ||
unless email_address.end_with?("#domain1.com") || email_address.end_with?("#domain2.com")
This may be a bit easier to read since both sides of the || don't have to be negated with !.
If more domains are added, then the repetitive email_address.end_with? is getting boring real fast. Alternative:
if ["#domain1.com", "#domain2.com"].none?{|domain| email_address.end_with?(domain)}
#do something
end
I forgot end_with? takes multiple arguments:
unless email_address.end_with?("#domain1.com", "#domain2.com")
#do something
end
How about:
(!email_address[/#domain[12]\.com\z/])
Related
Is this a valid way to impose a condition on a statement? I was having trouble using multiple &&'s or ||'s when using it in one line the other day.
#sales_opportunities << auction unless auction.company == current_user || !(auction.bids & current_user.bids).empty? || !auction.condition.include?(part.condition)
Some thoughts:
You can certainly put multiple conditions into one line after "unless"
If you do so, you may need to confirm they return the proper results, even with edge cases (make sure that the || or && has the proper scope, you may want parens to be explicit)
Nonetheless, this is pretty hard to read. I would suggest pulling those conditionals out and making each into its own method. This will make it more readable, and if you need those conditions elsewhere, it will make your code more DRY.
What #CaptainChaos and #PascalBetz said. At the very minimum, extract parts of that condition to local vars with descriptive names. Something like this:
insider_user = auction.company == current_user
user_placed_bids = (auction.bids & current_user.bids).present?
part_matches = auction.condition.include?(part.condition)
#sales_opportunities << auction unless insider_user || user_placed_bids || !part_matches
Now this looks much more manageable, heh?
I know Ruby supports a suffix if like:
number = -42 if opposite
but what's the purpose of this? Why would it be used in place of the prefix if statement?
The suffix-style if and unless can also be good for "guard clauses", in the form of:
return if ...
return unless ...
Here's an example:
# suffix-style
def save
return false if invalid?
# go for it
true
end
Versus:
# indented style
def save
if valid?
# go for it
true
else
false
end
end
In the second example, the entire implementation of the method has to be shifted over by one indent due to the valid? check, and we need an extra else clause. With the suffix style, the invalid? check is considered an edge case that we handle and then bail out, and the rest of the method doesn't need an indent or an else clause.
This is sometimes called a "guard clause" and is recommended by the Ruby Style Guide.
It can make the code easier to read in some cases. I find this to be true especially in the case of unless, where you have some action you usually want to perform:
number = -42 unless some_unusual_circumstance_holds
Once you have it for unless, for symmetry it makes sense to support it for if as well.
number = -42 if opposite
is the same as
if opposite
number = -42
end
Some people prefer the one-liner for readability reasons. Imagine a line like:
process_payment if order_fulfilled?
Doesn't that read nice?
Postfix style does not have the else section. It is useful when you only want to do something with one of the two cases divided by the condition and don't want to mess with the other case.
It's the same as prefix but shorter. The only reason is to save vertical space in the text editor.
I apologize if this question is answered somewhere but I'm not positive I'm phrasing it right for Google, and I haven't seen it in any style guides.
Since Ruby has multiple ways to show negativity in a conditional, what is the preferred way to write a conditional that is checking that one part is true and one part is false? Example:
if array && !array.include?('Bob')
#do stuff!
But you could also say:
if array
#do stuff! unless array.include?('Bob')
or:
if array && not array.include?('Bob')
#do stuff
or:
if !array.nil? && !array.include?('Bob')
or a wacky double unless:
unless array.nil?
#do stuff unless array.include?('Bob')
And several others. Any idea which is considered the most Rubyish? Sources to back your opinion up?
As far as documented guidelines, the only thing that i can think of is the Google guide that admonishes "don't use and and or; always use && and || instead.".
Other than that, it somewhat depends on the context. If all you have is code to be executed if one condition is true and the other false, then I would definitely put them in a single if with && !:
if array && !array.include?('Bob')
#do stuff!
On the other hand, you might have additonal code that gets executed if the first condition is true even if the second one is also true; in that case, the nested unless or if makes sense:
if array
do stuff! unless array.include? 'Bob'
do other stuff anyway
end
Does not improve readability, but still interesting.
If you use Rails you can use ActiveSupport try extension like this:
if array.try(:include?, 'Bob')
# Do stuff
I understand the difference between them, but I can't work out why they're both included in the language. Surely having both just causes confusion?
Their precedence is different, so they are not equivalent.
My rule of thumb is as follows: use && for logical expressions and use and for control flow.
Examples
# logical expressions
if user.first_name == 'Bob' && user.last_name == 'Jones'
# control flow
worker.do_this and worker.and_also_do_this_if_that_went_well
Perl has the same doublets, even with the same precedence difference as in Ruby.
Ruby was strongly influenced by Perl.
I believe one should look no further.
Do go through this:
http://phrogz.net/ProgrammingRuby/language.html#andornotanddefined
This is the best explanation I've seen:
http://avdi.org/devblog/2010/08/02/using-and-and-or-in-ruby/
Which way of writing this condition is better?
1)
(self.expense_gl_dist_code.dist_type == GlDistCode::PERCENTAGE || self.expense_gl_dist_code.dist_type == GlDistCode::MIXED)
2)
["GlDistCode::PERCENTAGE","GlDistCode::MIXED"].include?(self.expense_gl_dist_code.dist_type)
I find the second clearer for two reasons:
1) In the second version the elements being checked for are all next to each other, separated by commas. In the first version there's always self.expense_gl_dist_code.dist_type ==, so it's less easy to scan them all at once.
2) In the second version it's immediately obvious that all elements are checked for the same condition, while in the first version it could say something like
dist_type == GlDistCode::PERCENTAGE || dist_type == GlDistCode::MIXED || dist_type != GlDistCode::WHATEVER
and you might not notice right away.
The first way is much clearer and therefore to be preferred to the slightly obfuscated second option.
If you are just comparing two elements, I'd say either is fine.
I'm more inclined to the second version, because you can then include all the elements you want to validate against into a single variable, and name it. For example
ALLOWED_TYPES = [GldDistCode::PERCENTAGE, GlDistCode::MIXED]
then
if ALLOWED_TYPES.include?(dist_type)
is more legible IMHO.
BTW, you're using strings ("GldDistCode::PERCENTAGE") instead of the actual value which you intended.