FHIRPath Model API

The FHIRPathModelData struct provides runtime metadata required by FHIRPath expression engines. This page documents every exported function and method with its full signature, description, and usage example.

FHIRPathModel

Returns the package-level singleton containing all FHIRPath metadata for this FHIR version.

Signature

func FHIRPathModel() *FHIRPathModelData

Returns

A pointer to the singleton FHIRPathModelData instance. This instance is initialized at package load time and is safe for concurrent read access.

Example

import "github.com/gofhir/models/r4/v2"

model := r4.FHIRPathModel()
// model is ready to use -- no initialization needed

ChoiceTypes

Returns the permitted FHIR type codes for a polymorphic (choice) element path. The path must be the base name without a type suffix.

Signature

func (m *FHIRPathModelData) ChoiceTypes(path string) []string

Parameters

• path – The base element path using dot notation, e.g., "Observation.value" (not "Observation.valueQuantity").

Returns

• A slice of type code strings representing the permitted types for this choice element.
• nil if the path is not a choice type or is unknown.

Example

model := r4.FHIRPathModel()

types := model.ChoiceTypes("Observation.value")
// ["Quantity", "CodeableConcept", "string", "boolean", "integer",
//  "Range", "Ratio", "SampledData", "time", "dateTime", "Period"]

types = model.ChoiceTypes("Patient.deceased")
// ["boolean", "dateTime"]

types = model.ChoiceTypes("Patient.name")
// nil -- not a choice type

TypeOf

Returns the FHIR type code for the given element path. Primitive types use lowercase ("string", "boolean", "dateTime"), complex types use PascalCase ("HumanName", "CodeableConcept").

Signature

func (m *FHIRPathModelData) TypeOf(path string) string

Parameters

• path – The element path using dot notation, e.g., "Patient.name", "Observation.status".

Returns

• The FHIR type code as a string.
• An empty string if the path is unknown.

Example

model := r4.FHIRPathModel()

model.TypeOf("Patient.name")              // "HumanName"
model.TypeOf("Patient.active")            // "boolean"
model.TypeOf("Observation.status")        // "code"
model.TypeOf("Observation.valueQuantity") // "Quantity"
model.TypeOf("Patient.contact")           // "BackboneElement"
model.TypeOf("Unknown.path")             // ""

ReferenceTargets

Returns the allowed target resource type names for a Reference or canonical element at the given path.

Signature

func (m *FHIRPathModelData) ReferenceTargets(path string) []string

Parameters

• path – The element path of a Reference-typed field, e.g., "Observation.subject".

Returns

• A slice of resource type names that are valid targets for this reference.
• nil if the path is not a reference or has no constrained targets.

Example

model := r4.FHIRPathModel()

targets := model.ReferenceTargets("Observation.subject")
// ["Device", "Group", "Location", "Patient"]

targets = model.ReferenceTargets("Observation.performer")
// ["CareTeam", "Organization", "Patient", "Practitioner", "PractitionerRole", "RelatedPerson"]

targets = model.ReferenceTargets("Patient.name")
// nil -- not a Reference field

ParentType

Returns the immediate parent type name in the FHIR type hierarchy.

Signature

func (m *FHIRPathModelData) ParentType(typeName string) string

Parameters

• typeName – A FHIR type name, e.g., "Patient", "Age", "DomainResource".

Returns

• The parent type name as a string.
• An empty string if the type has no parent (e.g., the root Element type) or is unknown.

Example

model := r4.FHIRPathModel()

model.ParentType("Patient")        // "DomainResource"
model.ParentType("DomainResource") // "Resource"
model.ParentType("Bundle")         // "Resource"
model.ParentType("Age")            // "Quantity"
model.ParentType("Quantity")       // "Element"
model.ParentType("Element")        // ""

IsSubtype

Reports whether child is the same type as, or a subtype of, parent in the FHIR type hierarchy. It walks the type2Parent chain from child upward until it either finds parent or reaches the root.

Signature

func (m *FHIRPathModelData) IsSubtype(child, parent string) bool

Parameters

• child – The type name to check.
• parent – The potential ancestor type name.

Returns

• true if child == parent or if child is a descendant of parent in the type hierarchy.
• false otherwise.

Example

model := r4.FHIRPathModel()

model.IsSubtype("Patient", "Patient")        // true  (same type)
model.IsSubtype("Patient", "DomainResource") // true
model.IsSubtype("Patient", "Resource")       // true
model.IsSubtype("Age", "Quantity")           // true
model.IsSubtype("Quantity", "Age")           // false (parent, not child)
model.IsSubtype("Patient", "Observation")    // false (siblings)

ResolvePath

Resolves an element path that may be defined elsewhere. Some FHIR element paths are defined on a shared backbone type and referenced from multiple resources. This method maps such paths to their canonical definition location.

Signature

func (m *FHIRPathModelData) ResolvePath(path string) string

Parameters

• path – The element path to resolve.

Returns

• The canonical path if the element is defined elsewhere.
• The original path unchanged if it is not remapped.

Example

model := r4.FHIRPathModel()

// Most paths resolve to themselves
resolved := model.ResolvePath("Patient.name")
// "Patient.name"

// Some paths may resolve to a shared definition
resolved = model.ResolvePath("Bundle.entry.resource")
// Returns the canonical definition path

IsResource

Reports whether the given type name is a FHIR resource type (as opposed to a data type or backbone element).

Signature

func (m *FHIRPathModelData) IsResource(typeName string) bool

Parameters

• typeName – The FHIR type name to check.

Returns

• true if the type is a resource (e.g., "Patient", "Bundle", "Observation").
• false if it is a data type (e.g., "HumanName", "CodeableConcept") or unknown.

Example

model := r4.FHIRPathModel()

model.IsResource("Patient")         // true
model.IsResource("Observation")     // true
model.IsResource("Bundle")          // true
model.IsResource("HumanName")       // false
model.IsResource("CodeableConcept") // false
model.IsResource("BackboneElement") // false