How to convert nested objects into json IN Ruby

JSON has gradually become a mainstream data exchange format on the Internet due to its simple and convenient data structure.

Before discussing the JSON Conversion Method for Nested objects, let's look at the simple ruby JSON conversion.
First, the ruby object is converted to a JSON string:

Copy codeThe Code is as follows:
Class Obj1

Def initialize (var1)

@ Var1 = var1

End

Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"var1" => @ var1}

}. To_json (*)

End

Def self. json_create (json_str)

New (json_str ["data"] ["var1"])

End

End

Obj1 = Obj1.new ("I am obj1 ")

# Obj1 to JSON string

Json_str = obj1.to _ json

Puts "JSON string of obj1 =#{ json_str }"

# JSON string to obj1

Obj11 = JSON. parse (json_str)

Puts "ob1 from json string =#{ obj11.var1 }"

The code above shows that there are three key points for the conversion between ruby and JSON string:

# The following two methods are available only when the json library is introduced. json adds the to_json (* a) method to the Hash object through the open class method, for open class in ruby, see Open-Closed Principle in programming languages that support the Open Class feature)
1) require 'json'

# Define the to_json (* a) method for converting an object to a JSON string. The implementation is to use the to_json (* a) method of the Hash object.
2) def to_json (*)

# Define the json_create method for constructing an object from JSON string. This method is a class method.
3) def self. json_create (json_str)

The preceding three points are the basic requirements for JSON string Conversion in Ruby.

The code execution result is:

Copy codeThe Code is as follows:
JSON string of obj1 = {"json_class": "Obj1", "data": {"var1": "I am obj1 "}}

Ob1 from json string = I am obj1

Now let's look at the JSON string Conversion of nested objects:

Copy codeThe Code is as follows:
#! /Usr/local/ruby/bin/ruby

Require 'json'

Class Obj1

Def initialize (var1)

@ Var1 = var1

End

Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"var1" => @ var1}

}. To_json (*)

End

Def self. json_create (json_str)

New (json_str ["data"] ["var1"])

End

Attr_reader: var1

End

Class Obj2

Def initialize (var2)

@ Var2 = var2

End

Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"var2" => @ var2}

}. To_json (*)

End

Def self. json_create (json_str)

New (json_str ["data"] ["var2"])

End

Attr_reader: var2

End

Class Obj

Def initialize (obj1, obj2)

@ Obj1 = obj1

@ Obj2 = obj2

End

Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"obj1" => @ obj1.to _ json, "obj2" => @ obj2.to _ json}

}. To_json (*)

End

Def self. json_create (json_str)

New (json_str ["data"] ["obj1"], json_str ["data"] ["obj2"])

End

Def to_s

"Hi, I am obj"

End

Attr_reader: obj1,: obj2

End

Obj1 = Obj1.new ("I am obj1 ")

Obj2 = Obj2.new ("I am obj2 ")

Obj = Obj. new (obj1, obj2)

Obj_json_str = obj. to_json

Puts "JSON string of obj =#{ obj_json_str }"

Obj_1 = JSON. parse (obj_json_str)

Puts "obj_1 from json string, obj1.class =#{ obj_1.obj1.class}, obj2.class =#{ obj_1.obj2.class }"

In the code above, the nested object is our inertial thinking, which first converts the object itself into a JSON string:

Copy codeThe Code is as follows:
"Data" => {"obj1" => @ obj1.to _ json, "obj2" => @ obj2.to _ json}

The above code output:

Copy codeThe Code is as follows:
JSON string of obj = {"json_class": "Obj", "data": {"obj1": "{\" json_class \ ": \" Obj1 \", \ "data \": {\ "var1 \": \ "I am obj1 \" }}", "obj2": "{\" json_class \": \ "Obj2 \", \ "data \": {\ "var2 \": \ "I am obj2 \"}}"}}

Obj_1 from json string, obj1.class = String, obj2.class = String

We noticed that after the nested object is converted to a JSON string, there is an additional backslash \:

Copy codeThe Code is as follows:
JSON string of obj = {"json_class": "Obj", "data": {"obj1": "{\" json_class \ ": \" Obj1 \", \ "data \": {\ "var1 \": \ "I am obj1 \" }}", "obj2": "{\" json_class \": \ "Obj2 \", \ "data \": {\ "var2 \": \ "I am obj2 \"}}"}}

After JSON string Conversion, the nested objects obj1 and obj2 in obj are of the String type, rather than the expected Obj1 and Obj2 types.

Copy codeThe Code is as follows:
Obj_1 from json string, obj1.class = String, obj2.class = String

In fact, this is an inertial thinking victim. nested objects do not need to call its to_json method.
Therefore, the to_json code of the Obj class is as follows:

Copy codeThe Code is as follows:
Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"obj1" => @ obj1.to _ json, "obj2" => @ obj2.to _ json}

}. To_json (*)

End

Corrected:

Copy codeThe Code is as follows:
Def to_json (*)

{

"Json_class" => self. class,

"Data" => {"obj1" => @ obj1, "obj2" => @ obj2}

}. To_json (*)

End

Then, run the code to see the expected output:

Copy codeThe Code is as follows:
JSON string of obj = {"json_class": "Obj", "data": {"obj1": {"json_class": "Obj1", "data ": {"var1": "I am obj1" }}, "obj2": {"json_class": "Obj2", "data": {"var2 ": "I am obj2 "}}}}

Obj_1 from json string = {"json_class" => "Obj", "data" => {"obj1" = >#, "obj2" => #}}