Change 'nil' using literal notation?

rubyonrails-talk
1

Does anybody know can you change the output 'nil' to a different string using literal notation? Besides constructor?

Hash_Name = Hash.new("Anything other than nil!")

Hash_name = {              "key" => "value" }("Anything other than nil!")

New at this, just wondering. Thanks in advance

2

= X will set value if it’s nil to X.

Does anybody know can you change the output ‘nil’ to a different string

using literal notation? Besides constructor?

Hash_Name = Hash.new(“Anything other than nil!”)

Hash_name = {

         "key" => "value"

}(“Anything other than nil!”)

New at this, just wondering. Thanks in advance

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3

ahh the Conditional Assignment Operator, thanks :slight_smile:

4

Todd Hartsfield wrote in post #1102378:

Does anybody know can you change the output 'nil' to a different string using literal notation? Besides constructor?

Hash_Name = Hash.new("Anything other than nil!")

Hash_name = {              "key" => "value" }("Anything other than nil!")

New at this, just wondering. Thanks in advance

As an aside, you do realize that naming your variable "Hash_Name" makes it a constant right?

Should be:

hash_name = Hash.new("Anything other than nil!")

If you really intended to make that new hash a constant then the convention is:

HASH_NAME = Hash.new("Anything other than nil!")

5

umm as long as a variable does not have special characters or a space in it, as far as I am aware I thought variables are case sensitive, but should work. The example above I see a variable needs to be ALL_CAPS or all_lowercase, you cannot HaVe_bOtH. Is that correct?

6

In ruby, any variable whose name starts with a capital letter becomes a constant.

7

Which implies there are actually constants in Ruby.

8

Jordan Bedwell is correct. Ruby’s constants are /meant/ to be not changed, but you can define a constant and change its value later. Ruby will produce a warning ‘already initialized constant’

Also note that your constant’s internal representation can be changed without triggering the warning.

1.9.3p374 :001 > Const = ‘a’

=> “a”

1.9.3p374 :002 > Const = ‘b’

(irb):2: warning: already initialized constant Const

=> “b”

1.9.3p374 :003 > Const = {a: ‘a’}

(irb):3: warning: already initialized constant Const

=> {:a=>“a”}

1.9.3p374 :005 > Const[:a] = ‘b’

=> “b”

9

I didn't know that, thank you!

10

The last is misleading. You have created a constant that points to an Hash object. However, the Hash object itself is not frozen. The values pointed to by the keys are not constant or frozen. You can add new keys to the Hash, change values, etc. But if you try to set Const to something else (any other object) it will again show the warning.

irb(main):025:0> Const={a: 'a'} {:a=>"a"} irb(main):026:0> Const[:a] = 'b' "b" irb(main):027:0> Const={A: 'A', B: 'B'} (irb):27: warning: already initialized constant Const {:A=>"A", :B=>"B"} irb(main):029:0> Const[:z] = 'Z' "Z" irb(main):030:0> Const {:A=>"A", :B=>"B", :z=>"Z"} irb(main):031:0>

11

Dheeraj Kumar wrote in post #1102510:

In ruby, any variable whose name starts with a capital letter becomes a constant.

In my previous post I was speaking more to the naming conventions used in Ruby. Variable names are lowercase_understored and constants are UPPER_CASE_UNDERSCORED.

The mechanics of Ruby don't enforce this convention, outside of presenting a warning when "constants" (any variable name starting with an uppercase letter) are changed after initialization.

12

Convention doesn't equal required. The only reliably enforced "convention" is that classes must begin with a capital letter, it does not enforce CamalCase, it does not prevent Capital_Snake_Case. Ruby does not even disallow CamelConstants (even though technically classes are constants.)

13

Sorry, classes should be constants.

14

Jordon Bedwell wrote in post #1102618: