showing following error 
INPUT
alice,22&india,farhan@28#akhtar@34
←**[31mRuby exception occurred: undefined method `[]=' for nil:NilClass {:level=>:**
error}←[0m
{
"message" => [
[0] "alice,22&india,farhan@28#akhtar@34\r"
],
"@version" => "1",
"@timestamp" => "2015-12-03T08:56:58.308Z",
"host" => "myhost",
"age" => "22&india",
"datafields" => "farhan@28#akhtar@34",
"dataclass" => {
"datclassname" => "alice"
},
"myarray" => [
[0] {
"farhan" => 28
},
[1] {
"akhtar" => 34
}
],
"tags" => [
[0] "_rubyexception"
]
}
**my configuration file is **
input {
stdin
{
codec => plain
}
}
filter {
csv {
columns => ["dataclassname", "age","datafields"]
separator => ","
}
mutate
{
rename=>
{
"dataclassname" =>"[dataclass][datclassname]"
}
}
ruby {
code => '
b = event["datafields"].split("#");
ary = Array.new;
for c in b;
keyvar = c.split("@")[0];
valuevar = c.split("@")[1];
d = "{key : " << keyvar << ", value : " << valuevar << "}";
ary.push({ keyvar => valuevar.to_i });
end;
event["myarray"] = ary;
'
}
ruby {
code => "
event['myarray'].each { |m|
m.each_pair { |k, v|
event['dataclass']['fields'][k] = v
}
}
"
}
}
output {
stdout { codec => rubydebug }
}