问题
When I'm running a simple Ruby script, what's the easiest way to dump an object's fields to the console?
I'm looking for something similar to PHP's print_r() that will work with arrays as well.
回答1:
Possibly:
puts variable.inspect
回答2:
You might find a use for the methods method which returns an array of methods for an object. It's not the same as print_r, but still useful at times.
>> "Hello".methods.sort
=> ["%", "*", "+", "<", "<<", "<=", "<=>", "==", "===", "=~", ">", ">=", "[]", "[]=", "__id__", "__send__", "all?", "any?", "between?", "capitalize", "capitalize!", "casecmp", "center", "chomp", "chomp!", "chop", "chop!", "class", "clone", "collect", "concat", "count", "crypt", "delete", "delete!", "detect", "display", "downcase", "downcase!", "dump", "dup", "each", "each_byte", "each_line", "each_with_index", "empty?", "entries", "eql?", "equal?", "extend", "find", "find_all", "freeze", "frozen?", "grep", "gsub", "gsub!", "hash", "hex", "id", "include?", "index", "inject", "insert", "inspect", "instance_eval", "instance_of?", "instance_variable_defined?", "instance_variable_get", "instance_variable_set", "instance_variables", "intern", "is_a?", "is_binary_data?", "is_complex_yaml?", "kind_of?", "length", "ljust", "lstrip", "lstrip!", "map", "match", "max", "member?", "method", "methods", "min", "next", "next!", "nil?", "object_id", "oct", "partition", "private_methods", "protected_methods", "public_methods", "reject", "replace", "respond_to?", "reverse", "reverse!", "rindex", "rjust", "rstrip", "rstrip!", "scan", "select", "send", "singleton_methods", "size", "slice", "slice!", "sort", "sort_by", "split", "squeeze", "squeeze!", "strip", "strip!", "sub", "sub!", "succ", "succ!", "sum", "swapcase", "swapcase!", "taguri", "taguri=", "taint", "tainted?", "to_a", "to_f", "to_i", "to_s", "to_str", "to_sym", "to_yaml", "to_yaml_properties", "to_yaml_style", "tr", "tr!", "tr_s", "tr_s!", "type", "unpack", "untaint", "upcase", "upcase!", "upto", "zip"]
回答3:
The to_yaml method seems to be useful sometimes:
$foo = {:name => "Clem", :age => 43}
puts $foo.to_yaml
returns
---
:age: 43
:name: Clem
(Does this depend on some YAML module being loaded? Or would that typically be available?)
回答4:
p object
Ruby doc for p.
p(*args) public
For each object, directly writes obj.inspect followed by a newline to the program’s standard output.
回答5:
If you're looking for just the instance variables in the object, this might be useful:
obj.instance_variables.map do |var|
puts [var, obj.instance_variable_get(var)].join(":")
end
or as a one-liner for copy and pasting:
obj.instance_variables.map{|var| puts [var, obj.instance_variable_get(var)].join(":")}
回答6:
puts foo.to_json
might come in handy since the json module is loaded by default
回答7:
If you want to print an already indented JSON:
require 'json'
...
puts JSON.pretty_generate(JSON.parse(object.to_json))
回答8:
I came across this thread because I was looking for something similar. I like the responses and they gave me some ideas so I tested the .to_hash method and worked really well for the use case too. soo:
object.to_hash
回答9:
object.attributes_name
=> ["id", "name", "email", "created_at", "updated_at", "password_digest", "remember_token", "admin", "marketing_permissions", "terms_and_conditions", "disable", "black_list", "zero_cost", "password_reset_token", "password_reset_sent_at"]
object.attributes.values
=> [1, "tom", "tom@tom.com", Tue, 02 Jun 2015 00:16:03 UTC +00:00, Tue, 02 Jun 2015 00:22:35 UTC +00:00, "$2a$10$gUTr3lpHzXvCDhVvizo8Gu/MxiTrazOWmOQqJXMW8gFLvwDftF9Lm", "2dd1829c9fb3af2a36a970acda0efe5c1d471199", true, nil, nil, nil, nil, nil, nil, nil]
来源：https://stackoverflow.com/questions/354547/how-do-i-dump-an-objects-fields-to-the-console