Cast to MAP Types

MAP type is used to store and process key-value pair data, which can contain various basic types of keys and values, and can also nest other complex types.

Cast to MAP

FROM String

Behavior Change

Before version 4.0, some strings that didn't meet the MAP format might be converted normally (for example, '{1:1,2}'). Starting from version 4.0, strings that don't meet the MAP format will report an error in strict mode and return NULL in non-strict mode.

Strict Mode

BNF Definition

<map>          ::= "{" <map-content>? "}" | <empty-map> 

<empty-map>    ::= "{}"

<map-content>  ::=  <key-token> <map_key_delimiter> <value-token>
                     (<collection-delim> <key-token> <map_key_delimiter> <value-token>)*

<key-token>    ::= <whitespace>* "\"" <inner-sequence> "\"" <whitespace>*
                   | <whitespace>* "'" <inner-sequence> "'" <whitespace>*
                   | <whitespace>* <inner-sequence> <whitespace>*
<value-token>  ::= <key-token>

<inner-sequence>    ::= .*
<collection-delim>  ::= "," 
<map_key_delimiter> ::= ":"

Rule Description

1. The textual representation of a MAP must begin with a left brace { and end with a right brace }.
2. Empty MAPs are directly represented as {}.
3. Key-value pairs within the MAP are separated by commas ,.
4. Each key-value pair consists of a key, a colon :, and a value, in the order "key:value".
5. Keys and values can optionally be enclosed in matching single quotes (') or double quotes ("). The content inside the quotes is treated as a single entity.
6. Whitespace is allowed before and after elements within the MAP.
7. During parsing, parts that match <key-token> continue to apply the parsing rules of type K; parts that match <value-token> continue to apply the parsing rules of type V. These applied BNF rules and parsing logic are still considered part of the current MAP<K, V>'s BNF and parsing logic, with corresponding error handling and result transfer to the current MAP<K, V>'s behavior and results.
8. Elements can use "null" to represent a null value.

If the MAP format is not met, or if the key/value in key-value pairs does not meet the format of the corresponding type, an error is reported.

Examples

Input String	Conversion Result	Comment
"{}"	{}	Valid empty MAP
" {}"	Error	Does not start with a brace, parsing fails
'{123:456}'	Cast to MAP<int,int>: {123:456}	Valid MAP
'{123:null}'	Cast to MAP<int,int>: {123:null}	Valid MAP containing null value
'{ 123 : 456 }'	Cast to MAP<int,int>: {123:456}	Valid MAP with whitespace
'{"123":"456"}'	Cast to MAP<int,int>: {123:456}	Valid MAP using quotes
'{ "123":"abc" }'	Error	"abc" cannot be converted to int type
'{ 1:2 ,34, 5:6}'	Error	Does not meet MAP format

Non-Strict Mode

BNF Definition

<map>          ::= "{" <map-content>? "}" | <empty-map> 

<empty-map>    ::= "{}"

<map-content>  ::=  <key-token> <map_key_delimiter> <value-token>
                     (<collection-delim> <key-token> <map_key_delimiter> <value-token>)*

<key-token>    ::= <whitespace>* "\"" <inner-sequence> "\"" <whitespace>*
                   | <whitespace>* "'" <inner-sequence> "'" <whitespace>*
                   | <whitespace>* <inner-sequence> <whitespace>*
<value-token>  ::= <key-token>

<inner-sequence>    ::= .*
<collection-delim>  ::= "," 
<map_key_delimiter> ::= ":"

Rule Description

1. The textual representation of a MAP must begin with a left brace { and end with a right brace }.
2. Empty MAPs are directly represented as {}.
3. Key-value pairs within the MAP are separated by commas ,.
4. Each key-value pair consists of a key, a colon :, and a value, in the order "key:value".
5. Keys and values can optionally be enclosed in matching single quotes (') or double quotes ("). The content inside the quotes is treated as a single entity.
6. Whitespace is allowed before and after elements within the MAP.
7. During parsing, parts that match <key-token> continue to apply the parsing rules of type K; parts that match <value-token> continue to apply the parsing rules of type V. These applied BNF rules and parsing logic are still considered part of the current MAP<K, V>'s BNF and parsing logic, with corresponding error handling and result transfer to the current MAP<K, V>'s behavior and results.
8. Elements can use "null" to represent a null value.

If the MAP format does not meet the BNF format above, NULL is returned. If key/value in key-value pairs does not meet the format of the corresponding type, the corresponding position is set to null.

Examples

Input String	Conversion Result	Comment
"{}"	{}	Valid empty MAP
" {}"	NULL	Does not start with a brace, parsing fails
'{123:456}'	Cast to MAP<int,int>: {123:456}	Valid MAP
'{123:null}'	Cast to MAP<int,int>: {123:null}	Valid MAP containing null value
'{ 123 : 456 }'	Cast to MAP<int,int>: {123:456}	Valid MAP with whitespace
'{"123":"456"}'	Cast to MAP<int,int>: {123:456}	Valid MAP using quotes
'{ "123":"abc" }'	Cast to MAP<int,int>: {123:null}	"abc" cannot be converted to int type, converted to null
'{ 1:2 ,34, 5:6}'	NULL	Does not meet MAP format

FROM MAP<Other Type>

Strict Mode

Rule Description

For each element in the MAP, a Cast from Other Type To Type is performed. The Cast is also in strict mode.

Examples

Input MAP	Conversion Result	Comment
{"123":"456"}	Cast to MAP<int,int>: {123:456}	"123" and "456" can be converted to Int
{"abc":"123"}	Error	"abc" cannot be converted to Int
{"123":null}	Cast to MAP<int,int>: {123:null}	The Cast result of null is still null

Non-Strict Mode

Rule Description

For each element in the MAP, a Cast from Other Type To Type is performed. The Cast is also in non-strict mode.

Examples

Input MAP	Conversion Result	Comment
{"123":"456"}	Cast to MAP<int,int>: {123:456}	"123" and "456" can be converted to Int
{"abc":"123"}	Cast to MAP<int,int>: {null:123}	"abc" cannot be converted to Int, converted to null
{"123":null}	Cast to MAP<int,int>: {123:null}	The Cast result of null is still null