variable name

[Rick Tan]

Is there a way in Ruby to use the content of a variable as the name of a
variable. For example

var1 = 'myVar'

i want to assign a value to 'myVar' by referencing var1. The name of
the variable can vary depending on the content of var1. Other
application include using a variable to hold the name of a class method
which i need to call in my code.

Thanks in advance

 

[Tim Hunter]

Is there a way in Ruby to use the content of a variable as the name of a
variable. For example

var1 = 'myVar'

i want to assign a value to 'myVar' by referencing var1. The name of
the variable can vary depending on the content of var1. Other
application include using a variable to hold the name of a class method
which i need to call in my code.

Thanks in advance

In general, no. Most of the time this problem can be solved by using a
hash. That is,

var1 = 'myVar'
hsh[var1] = value

In the specific case of calling a method whose name is in a variable,
use send:

var1 = 'my_method'
obj.send(var1, arg1, arg2,...)

 

[Eric I.]

Is there a way in Ruby to use the content of a variable as the name of a
variable.  For example

var1 = 'myVar'

i want to assign a value to 'myVar' by referencing var1.  The name of
the variable can vary depending on the content of var1.  Other
application include using a variable to hold the name of a class method
which i need to call in my code.

With eval you can do quite a bit:

====

v_name = "my_var"
v_value = "5"

eval "#{v_name} = #{v_value}"
eval "puts my_var"

# note: generates
error
puts my_var rescue puts "error"

my_var = 0 # now initialize the variable in current
binding

eval "#{v_name} = #{v_value}"
eval "puts my_var"

# no error
now
puts my_var

====

Eric

====

Are you interested in on-site Ruby or Ruby on Rails training
that uses well-designed, real-world, hands-on exercises?
http://LearnRuby.com

 

[Brian Candler]

Is there a way in Ruby to use the content of a variable as the name of a
variable. For example

var1 = 'myVar'

i want to assign a value to 'myVar' by referencing var1. The name of
the variable can vary depending on the content of var1.

If you're talking about "myVar" being the name of a *local* variable,
then usually this means you're trying to solve the wrong problem

The normal solution is for var1 to refer to one of the following.

(1) an instance variable of an object

var1 = '@foo'
val = obj.instance_variable_get(var1)
obj.instance_variable_set(var1, val + 1)

(You can omit 'obj.' if you're talking about instance variables of the
'self' object)

(2) a method name

var1 = "foo"
obj.send(var1, 2, 3) # same as obj.foo(2,3)

var1 = "foo="
obj.send(var1, 4) # same as obj.foo = 4

(3) a constant or a class name

var1 = "String"
klass = Object.const_get(var1)
str = klass.new # same as str = String.new

require 'net/http'
var1 = "HTTP"
klass = Net.const_get(var1)
klass.new(...) # same as Net::HTTP.new(...)

Other
application include using a variable to hold the name of a class method
which i need to call in my code.

For that you use "send":

MyClass.send(var1, arg, arg...)

HTH,

Brian.