* fix(binding): Expose validator engine used by the default Validator
- Add func ValidatorEngine for returning the underlying validator engine used
  in the default StructValidator implementation.
- Remove the function RegisterValidation from the StructValidator interface
  which made it immpossible to use a StructValidator implementation without the
  validator.v8 library.
- Update and rename test for registering validation
  Test{RegisterValidation => ValidatorEngine}.
- Update readme and example for registering custom validation.
- Add example for registering struct level validation.
- Add documentation for the following binding funcs/types:
  - Binding interface
  - StructValidator interface
  - Validator instance
  - Binding implementations
  - Default func
* fix(binding): Move validator engine getter inside interface
* docs: rm date cmd from custom validation demo
		
	
		
			
				
	
	
		
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			51 lines
		
	
	
		
			2.3 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
## Struct level validations
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Validations can also be registered at the `struct` level when field level validations
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don't make much sense. This can also be used to solve cross-field validation elegantly.
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Additionally, it can be combined with tag validations. Struct Level validations run after
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the structs tag validations.
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### Example requests
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```shell
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# Validation errors are generated for struct tags as well as at the struct level
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$ curl -s -X POST http://localhost:8085/user \
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	-H 'content-type: application/json' \
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	-d '{}' | jq
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{
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  "error": "Key: 'User.Email' Error:Field validation for 'Email' failed on the 'required' tag\nKey: 'User.FirstName' Error:Field validation for 'FirstName' failed on the 'fnameorlname' tag\nKey: 'User.LastName' Error:Field validation for 'LastName' failed on the 'fnameorlname' tag",
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  "message": "User validation failed!"
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}
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# Validation fails at the struct level because neither first name nor last name are present
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$ curl -s -X POST http://localhost:8085/user \
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    -H 'content-type: application/json' \
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	-d '{"email": "george@vandaley.com"}' | jq
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{
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  "error": "Key: 'User.FirstName' Error:Field validation for 'FirstName' failed on the 'fnameorlname' tag\nKey: 'User.LastName' Error:Field validation for 'LastName' failed on the 'fnameorlname' tag",
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  "message": "User validation failed!"
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}
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# No validation errors when either first name or last name is present
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$ curl -X POST http://localhost:8085/user \
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    -H 'content-type: application/json' \
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	-d '{"fname": "George", "email": "george@vandaley.com"}'
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{"message":"User validation successful."}
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$ curl -X POST http://localhost:8085/user \
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    -H 'content-type: application/json' \
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	-d '{"lname": "Contanza", "email": "george@vandaley.com"}'
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{"message":"User validation successful."}
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$ curl -X POST http://localhost:8085/user \
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    -H 'content-type: application/json' \
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	-d '{"fname": "George", "lname": "Costanza", "email": "george@vandaley.com"}'
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{"message":"User validation successful."}
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```
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### Useful links
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- Validator docs - https://godoc.org/gopkg.in/go-playground/validator.v8#Validate.RegisterStructValidation
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- Struct level example - https://github.com/go-playground/validator/blob/v8.18.2/examples/struct-level/struct_level.go
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- Validator release notes - https://github.com/go-playground/validator/releases/tag/v8.7
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