openmrs-esm-core

O3 Framework / useAppContext

Function: useAppContext()

Call Signature

useAppContext<T>(namespace): undefined | Readonly<T>

Defined in: packages/framework/esm-react-utils/src/useAppContext.ts:30

This hook is used to access a namespace within the overall AppContext, so that a component can use any shared contextual values. A selector may be provided to further restrict the properties returned from the namespace.

Type Parameters

T

T extends object = object

The type of the value stored in the namespace

Parameters

namespace

string

The namespace to load properties from

Returns

undefined | Readonly<T>

The current value registered under namespace, or undefined when the namespace has not yet been registered, was unregistered (e.g. the owning component unmounted), or is a blank string. Consumers should handle the undefined case explicitly rather than defaulting to {}, since an empty-object default can mask a genuinely missing namespace and hide bugs.

Examples

// load a full namespace
const patientContext = useAppContext<PatientContext>('patient');

// loads part of a namespace
const patientName = useAppContext<PatientContext, string | undefined>('patient', (state) => state.display);

Call Signature

useAppContext<T, U>(namespace, selector): undefined | Readonly<U>

Defined in: packages/framework/esm-react-utils/src/useAppContext.ts:60

This hook is used to access a namespace within the overall AppContext, so that a component can use any shared contextual values. A selector may be provided to further restrict the properties returned from the namespace.

Type Parameters

T

T extends object = object

The type of the value stored in the namespace

U

U = T

The return type of this hook which is mostly relevant when using a selector

Parameters

namespace

string

The namespace to load properties from

selector

(state) => Readonly<U>

An optional function which extracts the relevant part of the state

Returns

undefined | Readonly<U>

The selected value, or undefined when the namespace has not yet been registered, was unregistered (e.g. the owning component unmounted), or is a blank string. Consumers should handle the undefined case explicitly rather than defaulting to {}, since an empty-object default can mask a genuinely missing namespace and hide bugs.

Examples

// load a full namespace
const patientContext = useAppContext<PatientContext>('patient');

// loads part of a namespace
const patientName = useAppContext<PatientContext, string | undefined>('patient', (state) => state.display);

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