Capitalize only first character of string and leave others alone? (Rails)

I'm trying to get Rails to capitalize the first character of a string, and leave all the others the way they are. I'm running into a problem where "i'm from New York" gets turned into "I'm from new york."

What method would I use to select the first character?

Thanks

EDIT: I tried to implement what macek suggested, but I'm getting a "undefined method `capitalize'" error. The code works fine without the capitalize line. Thanks for the help!

def fixlistname!
  self.title = self.title.lstrip + (title.ends_with?("...") ? "" : "...")
  self.title[0] = self.title[0].capitalize
  errors.add_to_base("Title must start with \"You know you...\"") unless self.title.starts_with? 'You know you'
end

EDIT 2: Got it working. Thanks for the help!

EDIT 3: Wait, no I didn't... Here's what I have in my list model.

def fixlistname!
  self.title = self.title.lstrip + (title.ends_with?("...") ? "" : "...")
  self.title.slice(0,1).capitalize + self.title.slice(1..-1)
  errors.add_to_base("Title must start with \"You know you...\"") unless self.title.starts_with?  'You know you'
end

EDIT 4: Tried macek's edit, and still getting an undefined method `capitalize'" error. What could I be doing wrong?

def fixlistname!
  self.title = title.lstrip
  self.title += '...' unless title.ends_with?('...')
  self.title[0] = title[0].capitalize
  errors.add_to_base('Title must start with "You know you..."') unless title.starts_with?("You know you")
end

EDIT 5: This is weird. I'm able to get rid of the undefined method error by using the line below. The problem is that it seems to replace the first letter with a number. For example, instead of capitalizing the y in You, it turns the y into a 121

self.title[0] = title[0].to_s.capitalize

This should do it:

title = "test test"     
title[0] = title[0].capitalize
puts title # "Test test"

Titleize will capitalise every word. This line feels hefty, but will guarantee that the only letter changed is the first one.

new_string = string.slice(0,1).capitalize + string.slice(1..-1)

Update:

irb(main):001:0> string = "i'm from New York..."
=> "i'm from New York..."
irb(main):002:0> new_string = string.slice(0,1).capitalize + string.slice(1..-1)
=> "I'm from New York..."

You can use humanize. If you don't need underscores or other capitals in your text lines.

Input:

"i'm from New_York...".humanize

Output:

"I'm from new york..."

As of Rails 5.0.0.beta4 you can use the new String#upcase_firstmethod or ActiveSupport::Inflector#upcase_first to do it. Check this blog post for more info.

So

"i'm from New York...".upcase_first

Will output:

"I'm from New York..."

str = "this is a Test"
str.sub(/^./, &:upcase)
# => "This is a Test"

An object oriented solution:

class String
  def capitalize_first_char
    self.sub(/^(.)/) { $1.capitalize }
  end
end

Then you can just do this:

"i'm from New York".capitalize_first_char

str.sub(/./, &:capitalize)

Edit 2

I can't seem to replicate your trouble. Go ahead and run this native Ruby script. It generates the exact output your looking for, and Rails supports all of these methods. What sort of inputs are you having trouble with?

#!/usr/bin/ruby
def fixlistname(title)
  title = title.lstrip
  title += '...' unless title =~ /\.{3}$/
  title[0] = title[0].capitalize
  raise 'Title must start with "You know you..."' unless title =~ /^You know you/
  title
end

DATA.each do |title|
  puts fixlistname(title)
end

__END__
you know you something WITH dots ...
you know you something WITHOUT the dots
  you know you something with LEADING whitespace...
  you know you something with whitespace BUT NO DOTS
this generates error because it doesn't start with you know you

output

You know you something WITH dots ...
You know you something WITHOUT the dots...
You know you something with LEADING whitespace...
You know you something with whitespace BUT NO DOTS...
RuntimeError: Title must start with "You know you..."

Edit

Based on your edit, you can try something like this.

def fixlistname!
  self.title = title.lstrip
  self.title += '...' unless title.ends_with?('...')
  self.title[0] = title[0].capitalize
  errors.add_to_base('Title must start with "You know you..."') unless title.starts_with?("You know you")
end

Original

This will do the trick

s = "i'm from New York"
s[0] = s[0].capitalize
#=> I'm from New York

When trying to use String#capitalize on the whole string, you were seeing I'm from new york because the method:

Returns a copy of str with the first character converted to uppercase and the remainder to lowercase.

"hello".capitalize    #=> "Hello"
"HELLO".capitalize    #=> "Hello"
"123ABC".capitalize   #=> "123abc"

my_string = "hello, World"
my_string.sub(/\S/, &:upcase) # => "Hello, World"

No-one's mentioned gsub, which lets you do this concisely.

string.gsub(/^([a-z])/) { $1.capitalize }

Example:

 > 'caps lock must go'.gsub(/^(.)/) { $1.capitalize }
=> "Caps lock must go"

Most of these answers edit the string in place, when you are just formatting for view output you may not want to be changing the underlying string so you can use tap after a dup to get an edited copy

'test'.dup.tap { |string| string[0] = string[0].upcase }

If and only if OP would want to do monkey patching on String object, then this can be used

class String
  # Only capitalize first letter of a string
  def capitalize_first
    self.sub(/\S/, &:upcase)
  end
end

Now use it:

"i live in New York".capitalize_first #=> I live in New York

An even shorter version could be:

s = "i'm from New York..."
s[0] = s.capitalize[0]

Note that if you need to deal with multi-byte characters, i.e. if you have to internationalize your site, the s[0] = ... solution won't be adequate. This Stack Overflow question suggests using the unicode-util gem

Ruby 1.9: how can I properly upcase & downcase multibyte strings?

EDIT

Actually an easier way to at least avoid strange string encodings is to just use String#mb_chars:

s = s.mb_chars
s[0] = s.first.upcase
s.to_s

Rails starting from version 5.2.3 has upcase_first method.

For example, "my Test string".upcase_first will return My Test string.

Perhaps the easiest way.

s = "test string"
s[0] = s[0].upcase
# => "Test string"

"i'm from New York".camelize
=> "I'm from New York"

string = "i'm from New York"
string.split(/\s+/).each{ |word,i| word.capitalize! unless i > 0 }.join(' ')
# => I'm from New York