Dynamic object construction

[John Lam]

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I'm trying to create a new object where the class of the object is
parameterized. My current solution is to use eval():

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def create(class)

@obj =3D eval("#{class}.new()")

end

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Is there a better way of doing this to avoid the hit of eval()?

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Thanks,

-John

http://www.iunknown.com

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[Bill Atkins]

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If class is a a class name (a String):

@obj =3D Object.const_get(klass).new

Using "class" as a parameter name won't work - the standard is to use=20
"klass" instead.

Bill

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I'm trying to create a new object where the class of the object is
parameterized. My current solution is to use eval():
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def create(class)
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@obj =3D eval("#{class}.new()")
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end
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Is there a better way of doing this to avoid the hit of eval()?
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Thanks,
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-John
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http://www.iunknown.com
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=20

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Bill Atkins

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[George Moschovitis]

@obj = Object.const_get(klass).new

does this work if klass == My::Namespace::Klass ?

-g.

 

[Trans]

does this work if klass == My::Namespace::Klass ?

Assuming you mean the string value

klass = "My::Namespace::Klass"

The answer is No. One has to do:

klass = "Klass"
@obj = My::Namespace.const_get(klass).new

The namespace issue is problematic. One alternative is in Ruby Facets:

require 'facet/object/constant'

klass == "My::Namespace::Klass"
@obj = constant(klass).new

T.

 

[George Moschovitis]

The answer is No. One has to do:

klass = "Klass"
@obj = My::Namespace.const_get(klass).new

I was expecting the negative answer ;-)

One alternative is in Ruby Facets

Interesting, I 'll see how that works...

-g.

 

[Nicholas Seckar]

Assuming you mean the string value
klass = "My::Namespace::Klass"
The answer is No. One has to do...

Or the ever popular

klass.split('::').inject(Object) {|parent, name| parent.const_get(name)}