Views and Result Types

Result Type Views Overview

Views in Goa provide a powerful way to control how result types are rendered in responses. When a method returns a result type with views:

1. The service method includes an additional view parameter
2. A dedicated views package is generated at the service level
3. View-specific validation logic is automatically generated

View Computation Process

Service Method Generation

When a method returns a result type with multiple views:

• The method signature includes an extra view parameter
• The generated endpoint function uses this view to create a viewed result type
• Constructors are generated to convert between regular and viewed result types

Views Package

The generated views package at the service level contains:

• Viewed result type definitions for each method result
• Fields use pointers to enable view-specific validation
• Conversion functions between regular and viewed result types

Marshalling and Transport

Server-Side Response

1. The viewed result type is marshalled into a server type
2. Nil attributes are omitted from the response
3. The view name is passed in the “Goa-View” header

Client-Side Response

1. Response is unmarshalled into the client type
2. Transformed into the viewed result type
3. View name is extracted from the “Goa-View” header
4. View-specific validation is performed
5. Viewed result type is converted back to service result type

Default View Behavior

• If no views are defined, Goa adds a “default” view automatically
• To bypass view-specific logic, use the Type DSL instead of result type
• The default view includes all basic fields of the result type

Best Practices

• Use views to control data visibility for different contexts
• Consider performance implications when designing views
• Document view behavior in your API specification
• Use meaningful view names that reflect their purpose