Ruby-on-rails – How to force gem to upgrade to gem 1.3.1

rubyruby-on-railsrubygems

I am trying to install a gem like this:

C:\InstantRails\rails_apps\foodmarksthespot>ruby script/plugin install git://github.com/lazyatom/engines.git

Which returns this message:

Rails requires RubyGems >= 1.3.1 (you have 1.2.0). Please `gem update --system` and try again.

But when I try to update using:

gem update --system

it says:

Updating RubyGems
Nothing to update

This is on windows. How can I force it to upgrade the system to a specific version?

Best Solution

http://rubyforge.org/forum/forum.php?forum_id=28071

From there:

NOTE: RubyGems 1.1 and 1.2 have problems upgrading when there is no
rubygems-update installed. You will need to follow the second set of update
instructions if you see "Nothing to update".

If you have an older version of RubyGems installed, then you can still
do it in two steps:

$ gem install rubygems-update (again, might need to be admin/root)
$ update_rubygems (... here too)

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Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

.nil? can be used on any object and is true if the object is nil.

.empty? can be used on strings, arrays and hashes and returns true if:

String length == 0
Array length == 0
Hash length == 0

Running .empty? on something that is nil will throw a NoMethodError.

That is where .blank? comes in. It is implemented by Rails and will operate on any object as well as work like .empty? on strings, arrays and hashes.

nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false

.blank? also evaluates true on strings which are non-empty but contain only whitespace:

"  ".blank? == true
"  ".empty? == false

Rails also provides .present?, which returns the negation of .blank?.

Array gotcha: blank? will return false even if all elements of an array are blank. To determine blankness in this case, use all? with blank?, for example:

[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true

Ruby – How to write a switch statement in Ruby

Ruby uses the case expression instead.

case x
when 1..5
  "It's between 1 and 5"
when 6
  "It's 6"
when "foo", "bar"
  "It's either foo or bar"
when String
  "You passed a string"
else
  "You gave me #{x} -- I have no idea what to do with that."
end

Ruby compares the object in the when clause with the object in the case clause using the === operator. For example, 1..5 === x, and not x === 1..5.

This allows for sophisticated when clauses as seen above. Ranges, classes and all sorts of things can be tested for rather than just equality.

Unlike switch statements in many other languages, Ruby’s case does not have fall-through, so there is no need to end each when with a break. You can also specify multiple matches in a single when clause like when "foo", "bar".

Best Solution

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Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

Ruby – How to write a switch statement in Ruby

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