Parsing

What is schema.Parse()?

To validate and parse your data into a destination pointer you can use the schema.Parse() function. The function signature looks like this:

schema.Parse(data, &dest, options...)

This works with any Zog Schema:

// string
var dest string
z.String().Min(3).Parse("test", &dest)
// structs
var dest User
z.Struct(z.Schema{"name": z.String().Min(3)}).Parse(map[string]any{"name": "test"}, &dest)

Under the hood Zog follows the Parsing Execution Structure and does a bunch of things under the hood to make sure your data is parsed correctly. Such as checking for zero values, coercing types, etc...

Parsing Struct Tags

By default zog will use the schema field name as the key for the parsed value. For example:

type User struct {
	Name string `zog:"name"`
}
z.Struct(z.Schema{"name": z.String()}).Parse(map[string]any{"name": "test"}, &User{}) // note zog will fetch the value as map[name]
type User struct {
   Name string `zog:"name"`
}
z.Struct(z.Schema{"Name": z.String()}).Parse(map[string]any{"name": "test"}, &User{}) // note zog will fetch the value as map[Name]

However, this is not always practical. For example, you may have data coming in in kebab case and you want to parse it into camel case. For this Zog supports a few struct tags:

• json tag which works for JSON input data
• form tag which works for form input data
• query tag which works for query string input data
• env tag which works for environment variables see zenv for more info
• zog a catch all tag which works for any input data

The priority of keys is as follows: json || form || query || env -> zog -> schema field name

You can mix and match without issue:

type User struct {
   Name string `zog:"first-name"`
   LastName string `query:"last_name" json:"last-name"`
}
z.Struct(z.Schema{"name": z.String(), "lastName": z.String()}).Parse(map[string]any{"first-name": "test", "lastName": "Doe"}, &User{})

Coercion

Zog will attempt to coerce the data into the correct type. For example if you have a z.Int() schema and you pass in a "1" it will be coerced into an int type. This behaviour, like almost everything else in Zog, can be customized. Zog provides two main ways to customize coercion:

• Global Coercion - Change the default coercion behaviour for all schemas. More details on this in the configuration page.
• Per schema coercers - Define custom coercion functions for your schemas.

Per schema coercers

You can define custom coercion functions for your schemas by using the z.WithCoercer() schema option.

z.String(z.WithCoercer(func(data any) (any, error) {
   return "test", nil // now the result will be "test" no matter the input
})).Parse("abc", &dest) // dest will be "test"

Parsing Execution Structure

1. Pretransforms
   • On error all parsing and validation stops and ZogIssues are returned.
   • Can be caught by catch
2. Default Check -> Assigns default value if the value is nil value
3. Optional Check -> Stops validation if the value is nil value
4. Casting -> Attempts to cast the value to the correct type
   • On error all parsing and validation stops and ZogIssues are returned
   • Can be caught by catch
5. Required check ->
   • On error: aborts if the value is its nil value and returns a required ZogIssue.
   • Can be caught by catch
6. Tests -> Run all tests on the value (including required)
   • On error: validation ZogIssues are added to the ZogIssueList or ZogIssueMap. All validation functions are run even if one of them fails.
   • Can be caught by catch
7. PostTransforms -> Run all postTransforms on the value.
   • On error you return: aborts and adds your error to the list of ZogIssues
   • Only run on valid values. Won't run if a ZogIssue was created before the postTransforms