Calling a Method From a String With the Method's Name in Ruby
RubyMetaprogrammingRuby Problem Overview
How can I do what they are talking about here, but in Ruby?
How would you do the function on an object? and how would you do a global function (see jetxee's answer on the post mentioned)?
EXAMPLE CODE:
event_name = "load"
def load()
puts "load() function was executed."
end
def row_changed()
puts "row_changed() function was executed."
end
#something here to see that event_name = "load" and run load()
UPDATE: How do you get to the global methods? or my global functions?
I tried this additional line
puts methods
and load and row_change where not listed.
Ruby Solutions
Solution 1 - Ruby
To call functions directly on an object
a = [2, 2, 3]
a.send("length")
# or
a.public_send("length")
which returns 3 as expected
or for a module function
FileUtils.send('pwd')
# or
FileUtils.public_send(:pwd)
and a locally defined method
def load()
puts "load() function was executed."
end
send('load')
# or
public_send('load')
Documentation:
Solution 2 - Ruby
send
/ call
/ eval
- and their Benchmarks
Three Ways: Typical invocation (for reference):
s= "hi man"
s.length #=> 6
send
Using s.send(:length) #=> 6
call
Using method_object = s.method(:length)
p method_object.call #=> 6
eval
Using eval "s.length" #=> 6
Benchmarks
require "benchmark"
test = "hi man"
m = test.method(:length)
n = 100000
Benchmark.bmbm {|x|
x.report("call") { n.times { m.call } }
x.report("send") { n.times { test.send(:length) } }
x.report("eval") { n.times { eval "test.length" } }
}
>...as you can see, instantiating a method object is the fastest dynamic way in calling a method, also notice how slow using eval is.
#######################################
##### The results
#######################################
#Rehearsal ----------------------------------------
#call 0.050000 0.020000 0.070000 ( 0.077915)
#send 0.080000 0.000000 0.080000 ( 0.086071)
#eval 0.360000 0.040000 0.400000 ( 0.405647)
#------------------------------- total: 0.550000sec
# user system total real
#call 0.050000 0.020000 0.070000 ( 0.072041)
#send 0.070000 0.000000 0.070000 ( 0.077674)
#eval 0.370000 0.020000 0.390000 ( 0.399442)
Credit goes to this blog post which elaborates a bit more on the three methods and also shows how to check if the methods exist.
Solution 3 - Ruby
Use this:
> a = "my_string"
> meth = a.method("size")
> meth.call() # call the size method
=> 9
Simple, right?
As for the global, I think the Ruby way would be to search it using the methods
method.
Solution 4 - Ruby
Personally I would setup a hash to function references and then use the string as an index to the hash. You then call the function reference with it's parameters. This has the advantage of not allowing the wrong string to call something you don't want to call. The other way is to basically eval
the string. Do not do this.
PS don't be lazy and actually type out your whole question, instead of linking to something.