Given strings like:
Bob
Bob,
Bob
Bob Burns,
How can you return that w/o a comma?
Bob
Bob
Bob
Bob Burns
Also, I would want this method not to break if passed a nil, just to return a nil?
def remove_trailing_comma(str)
!str.nil? ? str.replace(",") :nil
end
My thought would be to use string.chomp:
Returns a new String with the given record separator removed from the end of str (if present).
Does this do what you want?
def remove_trailing_comma(str)
str.nil? ? nil : str.chomp(",")
end
use String#chomp
irb(main):005:0> "Bob".chomp(",")
=> "Bob"
irb(main):006:0> "Bob,".chomp(",")
=> "Bob"
irb(main):007:0> "Bob Burns,".chomp(",")
=> "Bob Burns"
UPDATE:
def awesome_chomp(str)
str.is_a?(String) ? str.chomp(",") : nil
end
p awesome_chomp "asd," #=> "asd"
p awesome_chomp nil #=> nil
p awesome_chomp Object.new #=> nil
You could do something like this:
str && str.sub(/,$/, '')
As everyone said, chomp will do the trick.
Starting from Ruby 2.3 you can use the safe navigation operator like this: str&.chomp(','). It will only execute chomp if str is not nil, otherwise it will return nil.
you could use
str.delete_suffix(',')
Related
is there a built in way to get first match or nil for a character from string.
i can get a first character like this
'word'.match('o').to_s
but if there is no match it gives "" not nil
Use String#[match_str]:
If a match_str is given, that string is returned if it occurs in the string.
Returns nil if (...) the match string cannot be found.
'word'['o'] #=> 'o'
'word'['q'] #=> nil
The [] method is very versatile, you can also pass a regular expression or indices in different ways.
You can do it in such way:
'word'.scan('o').first #=> "o"
'word'.scan('e').first #=> nil
'word'.match(?o)[0] rescue nil
#=> "o"
'word'.match(?q)[0] rescue nil
#=> nil
'word'.match(/(o)/) && $1
#⇒ "o"
'word'.match(/(s)/) && $1
#⇒ nil
How can I replace characters from string without changing its object_id?
For example:
string = "this is a test"
The first 7 characters need to be replaced with capitalized characters like: "THIS IS a Test" and the object_id needs to be the same. In which way can I sub or replace the characters to make it happen?
You can do it like this:
string = "this is a test"
string[0, 7] = string[0, 7].upcase
With procedural languages, one might write the equivalent of:
string = "this is in jest"
string.object_id
#=> 70309969974760
(1..7).each { |i| string[i] = string[i].upcase }
#=> 1..7
string
#=> "tHIS IS in jest"
string.object_id
#=> 70309969974760
This is not very Ruby-like, but it does offer the advantage over #sawa's solution that it does not create a temporary 7-character string. (Well, it does create a one-character string.) This is unimportant for strings of reasonable length (and for those I'd certainly concur with sawa), but it could be significant for really, really, really long strings.
Another way to do this is as follows:
string.each_char.with_index { |c,i|
string[i] = string[i].upcase if (1..7).cover?(i) }
#=> "tHIS IS in jest"
string.object_id
#=> 70309969974760
This second way might be more efficient if string is not much larger than string[start_index..end_index].
Edit:
In a comment the OP indicates that the string is to be stripped, squeeze and reversed as well as certain characters converted to upper case. That could be done on the string in place, without creating a copy, as follows:
def strip_upcase_squeeze_reverse_whew(string, upcase_range, squeeze_str=nil)
string.strip!
upcase_range.each { |i| string[i] = string[i].upcase }
squeeze_str.nil? ? string.squeeze! : string.squeeze!(squeeze_str)
string.reverse!
end
I have assumed the four operations would be performed in a particular order, but if the order should be different, that's an easy fix.
string = " this may bee inn jest, butt it's alsoo a test "
string.object_id
#=> 70309970103280
strip_upcase_squeeze_reverse_whew(string, (1..7))
#=> "tset a osla s'ti tub ,tsej ni eb YAM SIHt"
string.object_id
#=> 70309970103280
The steps:
string = "this may bee inn jest, butt it's alsoo a test"
#=> "this may bee inn jest, butt it's alsoo a test"
upcase_range = (1..7)
#=> 1..7
string.strip!
#=> nil
string
#=> "this may bee inn jest, butt it's alsoo a test"
upcase_range.each { |i| string[i] = string[i].upcase }
#=> 1..7
string
#=> "tHIS MAY bee inn jest, butt it's alsoo a test"
squeeze_str.nil? ? string.squeeze! : string.squeeze!(squeeze_str)
#=> "tHIS MAY be in jest, but it's also a test"
string
#=> "tHIS MAY be in jest, but it's also a test"
string.reverse!
#=> "tset a osla s'ti tub ,tsej ni eb YAM SIHt"
Notice that in this example, strip! does not remove any characters, and therefore returns nil. Similarly, squeeze! would return nil if there is nothing to squeeze. It is for that reason that strip! and squeeze cannot be chained.
A second example:
string = " thiiiis may beeee in jeeest"
strip_upcase_squeeze_reverse_whew(string, (12..14), "aeiouAEIOU")
Adding onto a string without changing its object id:
foo = "foo"
# => "foo"
foo.object_id
# => 70196045363960
foo << "bar"
# => "foobar"
foo.object_id
# => 70196045363960
Replace an entire string without changing its object id
foo
# => "foo"
foo.object_id
# => 70196045363960
foo.gsub!(/./, '') << 'bar'
# => 'bar'
foo.object_id
# => 70196045363960
Replace part of a string without changing its object id
foo
# => "foo"
foo.object_id
# => 70196045363960
foo.gsub!(/o/, 'z')
# => 'fzz'
foo.object_id
# => 70196045363960
What's the most-efficient manner to remove beginning and ending spaces around a string, then convert the string to nil if the resulting value is zero-length?
For example:
> a=''
> squash(a)
=> nil
> a=' '
> squash(a)
=> nil
> a=' xyz '
> squash(a)
=> 'xyz'
> a=nil
> squash(a)
=> nil
Thus far:
def squash(value)
return nil if value.nil?
value.strip!
(value.blank? ? nil : value)
end
Seems like there could be a more-terse way of implementing this.
** edit **
While I am working in Rails, it would be nice if the answer would contain a Ruby-only implementation, too.
I should emphasize that the implementation needs to be able to handle a string with a nil value.
Assuming you want this for rails (otherwise blank? is undefined) you can use presence method:
def squash(value)
value && value.strip.presence
end
In pure ruby, I would do:
def squash(value)
return unless value
value = value.strip
value unless value.empty?
end
This will work with plain Ruby:
def squash(str)
str = str.to_s.strip
str unless str.empty?
end
Here's one way:
def squash(str)
(str && str[/\S/]) ? str.strip : nil
end
/\S/ looks for a character that is not whitespace.
squash " My dog has fleas. " #=> "My dog has fleas."
squash " " #=> nil
squash nil #=> nil
Reader challenge
I tried to also implement squash!, that would convert the argument str in place. If str is nil, just leave it alone. If str contains a least one non-whitespace character, then str.strip!. However, I could not figure out a way to convert a string to nil. I wanted to do this when the string is empty or contains only whitespace, but the problem is to convert any string, or more generally, any non-nil object, to nil, when the object is received as a method argument. Can it be done? [Edit: #Stefan says the type cannot be changed. I'm sure he's right, but I would like to see where that is written and understand why it is not permitted. Anyone? tidE].
This handles all your examples.
def squash(value)
value.to_s.strip.empty? ? nil : value.strip
end
Just adding this because it's short:
def squash(str)
str.to_s[/\S(.*\S)?/]
end
squash(nil) #=> nil
squash("") #=> nil
squash(" ") #=> nil
squash("a") #=> "a"
squash(" a") #=> "a"
squash("a ") #=> "a"
squash(" a ") #=> "a"
squash(" foo ") #=> "foo"
squash(" foo bar ") #=> "foo bar"
Here's a plain ruby version:
def squash(str)
str && str.strip! && (str unless str.empty?)
end
Update - If you want a version without side effects:
def squash(str)
str && (x = str.strip) && (x unless x.empty?)
end
If you want the method name squash with argument value.
def squash(value)
return value unless value.instance_of?(String)
return if value.strip!&.empty?
value
end
Features:
Works either on pure Ruby or Ruby on Rails
Works with other data types than string as well, for example, you can pass a number if you want
Testing:
squash('ok')
#=> ok
squash('')
#=> nil
squash(' ')
#=> nil
squash(' xyz ')
#=> 'xyz'
squash('xyz ')
#=> 'xyz'
squash(' xyz')
#=> 'xyz'
squash(123)
#=> 123
squash(nil)
#=> nil
Note:
I use safe navigation operator, which was released in Ruby 2.3.0. So make sure before using it.
irb(main):001:0> s = " string "
=> " string "
irb(main):002:0> s.strip!
=> "string"
irb(main):003:0> s.blank?
NoMethodError: undefined method `blank?' for "string":String
from (irb):3
from C:/RUBY/BIN/irb:12:in `'
irb(main):004:0>
I think blank is not Ruby but Rails? Anyway, what's wrong with
(value.length == 0 ? nil : value)
or even better
value.empty? ? nil : value
At least everybody would understand what the intention is here.
As I wrote in the title, I want to find if a string input consists of only one number.
Examples are
222 # true
33333 # true
22334 # false
556677 # false
I thought to use String#reverse but it fails with 556677.
if input == input.reverse
# do something
end
What is the best way?
Non-regex solution:
input.chars.uniq.size == 1
"222".chars.uniq.size == 1 #=> true
"556677".chars.uniq.size == 1 #=> false
You could use a regex like...
^(\d)\1*$
For example, this code...
strs = ['11211', '1', '111', '2222', '212']
strs.each {|str|
puts /^(\d)\1*$/.match(str)
}
...produces...
1
111
2222
Fiddle.
You could use String#squeeze followed by String#[] with a regex that matches a string consisting of a single digit:
"2222".squeeze[/^\d$/] #=> 2
"5566".squeeze[/^\d$/] #=> nil
"333a".squeeze[/^\d$/] #=> nil
"aaaa".squeeze[/^\d$/] #=> nil
The return value is either nil (falsy) or the unique digit (truey).
This is just a fun answer. In real life, I'd do it the way #alex has.
Why isnt that working:
>> s = "hi"
=> "hi"
>> s == ("hi"|"ho")
NoMethodError: undefined method `|' for "hi":String
from (irb):2
>>
I don't get it.. Is there a solution for this kind of syntax? Because
s == ("hi"|"ho")
#is shorther than
s == "hi" || s == "ho"
Yes, the bitwise operator | is not defined in the String class: http://ruby-doc.org/core/classes/String.html
Consider this for expressiveness:
["hi", "ho"].include? myStr
irb(main):001:0> s = "hi"
=> "hi"
irb(main):002:0> ["hi", "ho"]
=> ["hi", "ho"]
irb(main):003:0> ["hi", "ho"].include? s
=> true
irb(main):004:0> s = "foo"
=> "foo"
irb(main):005:0> ["hi", "ho"].include? s
=> false
In most high level languages that syntax will not work, you have to stick to the longer syntax of:
s == "hi" || s == "ho"
Note that | is a bitwise or, whereas || is a regular or
You could use the include? method on array if you've got several == tests to do:
["hi", "ho"].include?(s)
Not shorter for two checks admittedly but it will be shorter for three or more.
This syntax doesn't exist in any language as far as I know.
What you are saying
s == ("hi"|"ho")
Literally translates to 'bitwise OR the strings "hi" and "ho" together and then compare them with s'. If you can't see why this is not what you are looking for, try writing down the ASCII codes for "hi" and "ho" and then bitwise ORing them together. You are going to get complete gibberish.
You could make it work that way:
irb> class Pair
def initialize(strA,strB)
#strA,#strB = strA,strB
end
def ==(string)
string == #strA || string == #strB
end
def |(other)
Pair.new(self,other)
end
end
#=> nil
irb> class String
def |(other)
Pair.new(self,other)
end
alias old_equals :==
def ==(other)
if other.kind_of? Pair
other == self
else
old_equals other
end
end
end
#=> nil
irb> ("one"|"two") == "one"
#=> true
irb> ("one"|"two") == "two"
#=> true
irb> ("one"|"two") == "three"
#=> false
irb> "one" == ("one"|"two")
#=> true
irb> "three" == ("one"|"two"|"three")
#=> true
But since this involves some monkey-patching of a fairly lowlevel class, I wouldn't advise relying on it. Other people will hate reading your code.
Ruby supports binary 'or' and other binary operations on values of type Fixnum and Bignum, meaning any integer. Bitwise operations aren't supported on strings or any other type, as far as I know.
As other people have mentioned, you probably want something other than binary operations altogether. However, you can easily get integer representations of characters, so you can compare characters like so:
a = "Cake"
b = "Pie"
puts a[0] | b[0] # Prints "83" - C is 67 and P is 80.
You can get an array of the comparisons easily with some conversions.
a = "Cake"
b = "Pie " # Strings of uneven length is trivial but more cluttered.
a_arr = a.split(//)
b_arr = b.split(//)
c_arr = []
a.each_with_index { |char, i| c.push(a[i].to_i | b[i].to_i) }
# If you *really* want an ASCII string back...
c = c_arr.collect(&:chr).join
You could use a regex:
Like so:
regex = /hi|ho/
s = "hi"
t = "foo"
s =~ regex
#=> 0
t =~ regex
#=> nil