Modes.md

Oj Modes

Oj uses modes to switch the load and dump behavior. Initially Oj supported on the :object mode which uses a format that allows Ruby object encoding and decoding in a manner that lets almost any Ruby object be encoded and decoded without monkey patching the object classes. From that start other demands were made the were best met by giving Oj multiple modes of operation. The current modes are:

• :strict
• :null
• :compat or :json
• :rails
• :object
• :custom

Since modes determine what the JSON output will look like and alternatively what Oj expects when the Oj.load() method is called, mixing the output and input mode formats will most likely not behave as intended. If the object mode is used for producing JSON then use object mode for reading. The same is true for each mode. It is possible to mix but only for advanced users.

:strict Mode

Strict mode follows the JSON specifications and only supports the JSON native types, Boolean, nil, String, Hash, Array, and Numbers are encoded as expected. Encountering any other type causes an Exception to be raised. This is the safest mode as it is just simple translation, no code outside Oj or the core Ruby is execution on loading. Very few options are supported by this mode other than formatting options.

:null Mode

Null mode is similar to the :strict mode except that a JSON null is inserted if a non-native type is encountered instead of raising an Exception.

:compat or :json Mode

The :compat mode mimics the json gem. The json gem is built around the use of the to_json(*) method defined for a class. Oj attempts to provide the same functionality by being a drop in replacement with a few exceptions. To universally replace many JSON methods with their faster Oj counterparts, simply run Oj.mimic_json. {file:JsonGem.md} includes more details on compatibility and use.

:rails Mode

The :rails mode mimics the ActiveSupport version 5 encoder. Rails and ActiveSupport are built around the use of the as_json(*) method defined for a class. Oj attempts to provide the same functionality by being a drop in replacement with a few exceptions. {file:Rails.md} includes more details on compatibility and use.

:object Mode

Object mode is for fast Ruby object serialization and deserialization. That was the primary purpose of Oj when it was first developed. As such it is the default mode unless changed in the Oj default options. In :object mode Oj generates JSON that follows conventions which allow Class and other information such as Object IDs for circular reference detection to be encoded in a JSON document. The formatting follows the rules describe on the {file:Encoding.md} page.

:custom Mode

Custom mode honors all options. It provides the most flexibility although it can not be configured to be exactly like any of the other modes. Each mode has some special aspect that makes it unique. For example, the :object mode has it's own unique format for object dumping and loading. The :compat mode mimic the json gem including methods called for encoding and inconsistencies between JSON.dump(), JSON.generate(), and JSON(). More details on the {file:Custom.md} page.

:wab Mode

WAB mode ignores all options except the indent option. Performance of this mode is on slightly better than the :strict and :null modes. It is included to support the WABuR project. More details on the {file:WAB.md} page.

Options Matrix

Not all options are available in all modes. The options matrix identifies the options available in each mode. An x in the matrix indicates the option is supported in that mode. A number indicates the footnotes describe additional information.

Option	type	:null	:strict	:compat	:rails	:object	:custom	:wab
:allow_blank	Boolean			1	1		x
:allow_gc	Boolean	x	x	x	x	x	x
:allow_invalid_unicode	Boolean					x	x
:allow_nan	Boolean			x		x	x
:array_class	Class			x	x		x
:array_nl	String						x
:ascii_only	Boolean	x	x	2	2	x	x
:auto_define	Boolean					x	x
:bigdecimal_as_decimal	Boolean				3	x	x
:bigdecimal_load	Boolean						x
:compat_bigdecimal	Boolean			x			x
:cache_keys	Boolean	x	x	x	x		x
:cache_strings	Fixnum	x	x	x	x		x
:circular	Boolean	x	x	x	x	x	x
:class_cache	Boolean					x	x
:create_additions	Boolean			x	x		x
:create_id	String			x	x		x
:empty_string	Boolean						x
:escape_mode	Symbol						x
:float_precision	Fixnum	x	x				x
:hash_class	Class			x	x		x
:ignore	Array					x	x
:indent	Integer	x	x	4	4	x	x	x
:indent_str	String			x	x		x
:integer_range	Range	x	x	x	x	x	x	x
:match_string	Hash			x	x		x
:max_nesting	Fixnum	5	5	x		5	5
:mode	Symbol	-	-	-	-	-	-
:nan	Symbol						x
:nilnil	Boolean						x
:object_class	Class			x			x
:object_nl	String			x	x		x
:omit_nil	Boolean	x	x	x	x	x	x
:quirks_mode	Boolean			6			x
:safe	String			x
:second_precision	Fixnum					x	x
:space	String			x	x		x
:space_before	String			x	x		x
:symbol_keys	Boolean	x	x	x	x	x	x
:trace	Boolean	x	x	x	x	x	x	x
:time_format	Symbol					x	x
:use_as_json	Boolean						x
:use_raw_json	Boolean			x	x	x	x
:use_to_hash	Boolean						x
:use_to_json	Boolean						x

---

1. :allow_blank an alias for :nilnil.

2. The :ascii_only options is an undocumented json gem option.

3. By default the bigdecimal_as decimal is not set and the default encoding for Rails is as a string. Setting the value to true will encode a BigDecimal as a number which breaks compatibility. Note: after version 3.11.3 both Oj.generate and JSON.generate will not honour this option in Rails Mode, detais on ohler55#716.

4. The integer indent value in the default options will be honored by since the json gem expects a String type the indent in calls to 'to_json()', 'Oj.generate()', or 'Oj.generate_fast()' expect a String and not an integer.

5. The max_nesting option is for the json gem and rails only. It exists for compatibility. For other Oj dump modes the maximum nesting is set to over 1000. If reference loops exist in the object being dumped then using the :circular option is a far better choice. It adds a slight overhead but detects an object that appears more than once in a dump and does not dump that object a second time.

6. The quirks mode option is no longer supported in the most recent json gem. It is supported by Oj for backward compatibility with older json gem versions.