Turn json object to local and global variables, below is the code
require 'json'
hash = '{"$a":5,"b":10}'
hash1 = JSON.parse(hash)
hash1.each do |k,v|
singleton_class.send(:attr_accessor,k)
send(eval("#{k}=",v))
end
puts $a
Expected output:
5
Take this answer with a grain of salt because I'm no expert on Ruby's eval, but this worked for me:
require 'json'
hash = '{"$a":5,"b":10}'
hash1 = JSON.parse(hash)
bind = binding
hash1.each do |k,v|
# Dunno what this is for and things work fine without it.
# singleton_class.send(:attr_accessor,k)
# You don't want to call `send` here, just call `eval` directly.
eval("#{k}=#{v}", bind)
end
puts $a
# => 5
puts b
# => 10
Note that I'm passing in a binding from the parent scope to eval since you'll want to access local variables such as b in the parent scope after you exit the loop.
Lastly, v needed to be part of the string passed to eval, not the second parameter passed to eval, which, if anything, needs to be a binding. If you pass an integer it will raise an exception.
However, I should warn you that global variables should be used with restraint, and that using eval can be dangerous, especially if you get this JSON from someone else.
eval('foo="Bar"'); foo it indeed raises an exception. No surprise there. But the solution I used in my answer – passing in a binding to the parent context – should have worked. It doesn't with your example. Which makes me wonder why my answer works at all (which is another reason OP should take it with a grain of salt).Here is the another method which will work out for local and global variables. where global variable can be evaluated if the key starts with "$" ,else attribute accessor can take care of local variables.
require 'json'
hash = '{"$a":5,"b":10}'
hash1 = JSON.parse(hash)
bind = binding
hash1.each do |k,v|
if k.start_with?"$"
eval("#{k}=#{v}")
else
singleton_class.send(:attr_accessor,k)
send("#{k}=",v)
end
end
puts "#{$a} \n#{b}"
Output:
5
10
evalmakes me think if is there is a better way to do that and if this leads to a security vulnerability. Perhaps working directly with the hash would be a better idea?