Add a variable to a class instance at runtime: Difference between revisions
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(New page: {{task}} This demonstrates how to dynamically add variables to a class instance at runtime. This is useful when the methods/variables are based on a data file that isn't available until r...) |
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==[[Python]]== |
==[[Python]]== |
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[[Category:Python]] |
[[Category:Python]] |
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class empty(object): |
class empty(object): |
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pass |
pass |
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e = empty() |
e = empty() |
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setattr(e, "foo", 1) |
setattr(e, "foo", 1) |
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print e.foo |
print e.foo |
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==[[Ruby]]== |
==[[Ruby]]== |
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[[Category:Ruby]] |
[[Category:Ruby]] |
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class Empty |
class Empty |
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end |
end |
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e = Empty.new |
e = Empty.new |
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e.instance_variable_set("@foo", 1) |
e.instance_variable_set("@foo", 1) |
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e.instance_eval("class << self; attr_accessor :foo; end") |
e.instance_eval("class << self; attr_accessor :foo; end") |
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puts e.foo |
puts e.foo |
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Revision as of 00:06, 18 September 2007
You are encouraged to solve this task according to the task description, using any language you may know.
This demonstrates how to dynamically add variables to a class instance at runtime. This is useful when the methods/variables are based on a data file that isn't available until runtime. Hal Fulton gives an example of creating an OO CSV parser at An Exercise in Metaprogramming with Ruby
Python
class empty(object): pass
e = empty() setattr(e, "foo", 1) print e.foo
Ruby
class Empty
end
e = Empty.new
e.instance_variable_set("@foo", 1)
e.instance_eval("class << self; attr_accessor :foo; end")
puts e.foo