String to symbol

ruby-talk
1

Hi people,

Is there a way to "intern" a string so that it becomes denoted by a symbol?

Something like:

# This doesn't work as I wrote it, I know
:repetitive_message <= "blah blah blah"

puts :repetitive_message

TIA

···

--
Fernando Cacciola
SciSoft
http://fcacciola.50webs.com

2

Fernando Cacciola wrote:

Hi people,

Is there a way to "intern" a string so that it becomes denoted by a symbol?

Something like:

# This doesn't work as I wrote it, I know
:repetitive_message <= "blah blah blah"

puts :repetitive_message
puts :repetitive_message
puts :repetitive_message
puts :repetitive_message

If you use

puts :"blah blah blah"

then no matter how many times you write it, the symbol literal will
reference the same symbol (as long as the literal is the same, of
course). Also, you can assign either a simple string, or a symbol to a
variable, thus reusing it without repeating in the source.

my_str = "some string"
my_sym = :"some symbol"

puts my_str
puts my_sym

mortee

3

mortee wrote:

Fernando Cacciola wrote:

Hi people,

Is there a way to "intern" a string so that it becomes denoted by a
symbol?

Something like:

# This doesn't work as I wrote it, I know

repetitive_message <= "blah blah blah"

puts :repetitive_message

If you use

puts :"blah blah blah"

Ha.. I missed that you could prefix a string with ":" like that.

then no matter how many times you write it, the symbol literal will
reference the same symbol (as long as the literal is the same, of
course). Also, you can assign either a simple string, or a symbol to a
variable, thus reusing it without repeating in the source.

my_str = "some string"
my_sym = :"some symbol"

Right.
If I name the "variable" as "MY_STR" is then officially a "constant" (instead of a variable) right?
(and that would be preferred in this case)

···

--
Fernando Cacciola
SciSoft
http://fcacciola.50webs.com

4

Fernando Cacciola wrote:

mortee wrote:

my_str = "some string"
my_sym = :"some symbol"

Right.
If I name the "variable" as "MY_STR" is then officially a "constant"
(instead of a variable) right?
(and that would be preferred in this case)

If you wish. Note that you can't create constants from within methods.

mortee

5

mortee wrote:

Fernando Cacciola wrote:

mortee wrote:

my_str = "some string"
my_sym = :"some symbol"

Right.
If I name the "variable" as "MY_STR" is then officially a "constant"
(instead of a variable) right?
(and that would be preferred in this case)

If you wish. Note that you can't create constants from within methods.

Oh... why is that?

···

--
Fernando Cacciola
SciSoft
http://fcacciola.50webs.com

6

Fernando Cacciola wrote:

mortee wrote:

If you wish. Note that you can't create constants from within methods.

Oh... why is that?

I don't know the exact reason. I guess that constants are intended to be
assigned during the initialization phase of an application, while
modules and classes are defined. Methods are primarily used during the
actual normal operation of the program.

If you absolutely need to assign a constant from a method, e.g. because
you define a method for doing some meta-programming magic, and it needs
to create constants too, you can use Module#const_set.

mortee

7

If you wish. Note that you can't create constants from within methods.

I think what you mean is the dynamic constant assignment like so
def hi
  ABC = "hi"
end

But you can generate them programmatically like so:

def test(arg)
  _ = Object.const_set(arg.capitalize, "this is the constant
"+arg.capitalize)
end

test 'foo'
test 'bar'

puts Foo # "this is the constant Foo"
puts Bar # "this is the constant Bar"

I love constants btw I even abuse them and dont care that I do! :slight_smile:

···

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