API docs: context | LoopBack Documentation

Page Contents

context package

Classes

Class	Description
Binding	Binding represents an entry in the `Context`. Each binding has a key and a corresponding value getter.
BindingKey
Context	Context provides an implementation of Inversion of Control (IoC) container
ContextSubscriptionManager	Manager for context observer subscriptions
ContextView	`ContextView` provides a view for a given context chain to maintain a live list of matching bindings and their resolved values within the context hierarchy. This class is the key utility to implement dynamic extensions for extension points. For example, the RestServer can react to `controller` bindings even they are added/removed/updated after the application starts. `ContextView` is an event emitter that emits the following events: - ‘bind’: when a binding is added to the view - ‘unbind’: when a binding is removed from the view - ‘close’: when the view is closed (stopped observing context events) - ‘refresh’: when the view is refreshed as bindings are added/removed - ‘resolve’: when the cached values are resolved and updated
DefaultConfigurationResolver	Resolver for configurations of bindings
GenericInterceptorChain	A chain of generic interceptors to be invoked for the given context
InterceptedInvocationContext	A specialized InvocationContext for interceptors
InterceptionHandler	A proxy handler that applies interceptors See https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Proxy
InvocationContext	InvocationContext represents the context to invoke interceptors for a method. The context can be used to access metadata about the invocation as well as other dependencies.
ProxySource	Invocation source for injected proxies. It wraps a snapshot of the `ResolutionSession` that tracks the binding/injection stack.
ResolutionError	Error for context binding resolutions and dependency injections
ResolutionSession	Object to keep states for a session to resolve bindings and their dependencies within a context

Enumerations

Enumeration	Description
BindingCreationPolicy	Policy to control if a binding should be created for the context
BindingScope	Scope for binding values
BindingType	Type of the binding source

Functions

Function	Description
asBindingTemplate(scopeAndTags)	Convert binding scope and tags as a template function
asClassOrProvider(target)	A factory function to create a template function to bind the target class as a class or `Provider`.
asGlobalInterceptor(group)	The `BindingTemplate` function to configure a binding as a global interceptor by tagging it with `ContextTags.INTERCEPTOR`
asProvider(target)	A factory function to create a template function to bind the target class as a `Provider`.
asResolutionOptions(optionsOrSession)	Normalize ResolutionOptionsOrSession to ResolutionOptions
assertTargetType(injection, expectedType, expectedTypeName)	Assert the target type inspected from TypeScript for injection to be the expected type. If the types don’t match, an error is thrown.
bind(specs)	`@bind` is now an alias to for backward compatibility
bindingTemplateFor(cls, options)	Get the binding template for a class with binding metadata
compareBindingsByTag(phaseTagName, orderOfPhases)	Creates a binding compare function to sort bindings by tagged phase name.
compareByOrder(a, b, order)	Compare two values by the predefined order
composeInterceptors(interceptors)	Compose a list of interceptors as a single interceptor
config(propertyPath, metadata)	Inject a property from `config` of the current binding. If no corresponding config value is present, `undefined` will be injected as the configuration binding is resolved with `optional: true` by default.
configBindingKeyFor(key, propertyPath)	Create binding key for configuration of the binding
createBindingFromClass(cls, options)	Create a binding from a class with decorated metadata. The class is attached to the binding as follows: - `binding.toClass(cls)`: if `cls` is a plain class such as `MyController` - `binding.toProvider(cls)`: if `cls` is a value provider class with a prototype method `value()` - `binding.toDynamicValue(cls)`: if `cls` is a dynamic value provider class with a static method `value()`
createProxyWithInterceptors(target, context, session, source)	Create a proxy that applies interceptors for method invocations
createViewGetter(ctx, bindingFilter, session)	Create a context view as a getter with the given filter
createViewGetter(ctx, bindingFilter, bindingComparator, session)	Create a context view as a getter with the given filter and sort matched bindings by the comparator.
describeInjectedArguments(target, method)	Return an array of injection objects for parameters
describeInjectedProperties(target)	Return a map of injection objects for properties
filterByKey(keyPattern)	Create a binding filter from key pattern
filterByTag(tagPattern)	Create a binding filter for the tag pattern
getBindingMetadata(target)	Get binding metadata for a class
getDeepProperty(value, path)	Get nested properties of an object by path
globalInterceptor(group, specs)	`@globalInterceptor` decorator to mark the class as a global interceptor
hasInjections(cls)	Check if the given class has `@inject` or other decorations that map to `@inject`.
includesTagValue(itemValues)	Create a tag value matcher function that returns `true` if the target tag value equals to the item value or is an array that includes the item value.
inject(bindingSelector, metadata, resolve)	A decorator to annotate method arguments for automatic injection by LoopBack IoC container.
injectable(specs)	Decorate a class with binding configuration
inspectInjections(binding)	Inspect injections for a binding created with `toClass` or `toProvider`
inspectTargetType(injection)	Inspect the target type for the injection to find out the corresponding JavaScript type
instantiateClass(ctor, ctx, session, nonInjectedArgs)	Create an instance of a class which constructor has arguments decorated with `@inject`. The function returns a class when all dependencies were resolved synchronously, or a Promise otherwise.
intercept(interceptorOrKeys)	Decorator function `@intercept` for classes/methods to apply interceptors. It can be applied on a class and its public methods. Multiple occurrences of `@intercept` are allowed on the same target class or method. The decorator takes a list of `interceptor` functions or binding keys.
invokeInterceptors(context, interceptors)	Invoke a chain of interceptors with the context
invokeMethod(target, method, ctx, nonInjectedArgs, options)	Invoke a method using dependency injection. Interceptors are invoked as part of the invocation.
invokeMethodWithInterceptors(context, target, methodName, args, options)	Invoke a method with the given context
isBindingAddress(bindingSelector)	Type guard for binding address
isBindingTagFilter(filter)	Type guard for BindingTagFilter
isDynamicValueProviderClass(factory)	Check if the factory is a value factory provider class
isPromiseLike(value)	Check whether a value is a Promise-like instance. Recognizes both native promises and third-party promise libraries.
isProviderClass(cls)	Check if a class implements `Provider` interface
mergeInterceptors(interceptorsFromSpec, existingInterceptors)	Adding interceptors from the spec to the front of existing ones. Duplicate entries are eliminated from the spec side. For example: [log] + [cache, log] => [cache, log] - [log] + [log, cache] => [log, cache] - [] + [cache, log] => [cache, log] - [cache, log] + [] => [cache, log] - [log] + [cache] => [log, cache]
registerInterceptor(ctx, interceptor, options)	Register an interceptor function or provider class to the given context
removeNameAndKeyTags(binding)	A binding template function to delete `name` and `key` tags
resolveInjectedArguments(target, method, ctx, session, nonInjectedArgs)	Given a function with arguments decorated with `@inject`, return the list of arguments resolved using the values bound in `ctx`. The function returns an argument array when all dependencies were resolved synchronously, or a Promise otherwise.
resolveInjectedProperties(constructor, ctx, session)	Given a class with properties decorated with `@inject`, return the map of properties resolved using the values bound in `ctx`. The function returns an argument array when all dependencies were resolved synchronously, or a Promise otherwise.
resolveList(list, resolver)	Resolve entries of an array into a new array with the same indexes. If one or more entries of the source array are resolved to a promise by the `resolver` function, this method returns a promise which will be resolved to the new array with fully resolved entries.
resolveMap(map, resolver)	Resolve entries of an object into a new object with the same keys. If one or more entries of the source object are resolved to a promise by the `resolver` function, this method returns a promise which will be resolved to the new object with fully resolved entries.
resolveUntil(source, resolver, evaluator)	Resolve an iterator of source values into a result until the evaluator returns `true`
sortBindingsByPhase(bindings, phaseTagName, orderOfPhases)	Sort bindings by phase names denoted by a tag and the predefined order
transformValueOrPromise(valueOrPromise, transformer)	Transform a value or promise with a function that produces a new value or promise
tryCatchFinally(action, errorAction, finalAction)	Try to run an action that returns a promise or a value with error and final actions to mimic `try {} catch(err) {} finally {}` for a value or promise.
tryWithFinally(action, finalAction)	Try to run an action that returns a promise or a value
uuid()	A utility to generate uuid v4

Interfaces

Interface	Description
BindingComparator	Compare function to sort an array of bindings. It is used by `Array.prototype.sort()`.
BindingElement	Wrapper for bindings tracked by resolution sessions
BindingFilter	A function that filters bindings. It returns `true` to select a given binding.
BindingInspectOptions	Options for binding.inspect()
BindingTagFilter	Binding filter function that holds a binding tag pattern. `Context.find()` uses the `bindingTagPattern` to optimize the matching of bindings by tag to avoid expensive check for all bindings.
ConfigInjectionMetadata	Injection metadata for `@config.*`
ConfigurationResolver	Resolver for configuration of bindings. It’s responsible for finding corresponding configuration for a given binding key. By default, `undefined` is expected if no configuration is provided. The behavior can be overridden by setting `optional` to `false` in resolution options.
ContextInspectOptions	Options for context.inspect()
ContextObserver	Observers of context bind/unbind events
ContextViewEvent	An event emitted by a `ContextView`
DynamicValueProviderClass	A class with a static `value` method as the factory function for `toDynamicValue`.
InjectBindingMetadata	Metadata for `@inject.binding`
Injection	Descriptor for an injection point
InjectionDescriptor
InjectionElement	Wrapper for injections tracked by resolution sessions
InjectionMetadata	An object to provide metadata for `@inject`
Interceptor	Interceptor function to intercept method invocations
InterceptorBindingOptions	Options for an interceptor binding
InvocationSource	An interface to represent the caller of the invocation
JSONArray	JSON array
JSONObject	JSON object
Notification	Event data for observer notifications
Provider	Providers allow developers to compute injected values dynamically, with any dependencies required by the value getter injected automatically from the Context.
ResolutionContext	Contextual metadata for resolution
ResolutionOptions	Options for binding/dependency resolution
ResolverFunction	A function to provide resolution of injected values.
Subscription	Subscription of context events. It’s modeled after https://github.com/tc39/proposal-observable.
TagValueMatcher	A function to check if a given tag value is matched for `filterByTag`

Namespaces

Namespace	Description
bind	Alias namespace `bind` to `injectable` for backward compatibility It should have the same members as `bind`.
config
ContextBindings	Namespace for context bindings
ContextTags	Namespace for context tags
Getter
inject
injectable	A namespace to host shortcuts for `@injectable`

Variables

Variable	Description
ANY_TAG_VALUE	A symbol that can be used to match binding tags by name regardless of the value.
BINDING_METADATA_KEY	Metadata key for binding metadata
DEFAULT_TYPE_NAMESPACES
GLOBAL_INTERCEPTOR_NAMESPACE	Default namespace for global interceptors
INTERCEPT_CLASS_KEY	Metadata key for method-level interceptors
INTERCEPT_METHOD_KEY	Metadata key for method-level interceptors
LOCAL_INTERCEPTOR_NAMESPACE	Default namespace for local interceptors
UUID_PATTERN	A regular expression for testing uuid v4 PATTERN

Type Aliases

Type Alias	Description
AliasBindingSource	Binding source for `toAlias`
AsInterceptedFunction	The intercepted variant of a function to return `ValueOrPromise<T>`. If `T` is not a function, the type is `T`.
AsValueOrPromise	Create the Promise type for `T`. If `T` extends `Promise`, the type is `T`, otherwise the type is `ValueOrPromise<T>`.
AsyncProxy	The proxy type for `T`. The return type for any method of `T` with original return type `R` becomes `ValueOrPromise<R>` if `R` does not extend `Promise`. Property types stay untouched.
BindingAddress
BindingEvent	Information for a binding event
BindingEventListener	Event listeners for binding events
BindingFromClassOptions	Options to customize the binding created from a class
BindingMetadata	Binding metadata from `@injectable`
BindingScopeAndTags	An object to configure binding scope and tags
BindingSelector	Select binding(s) by key or a filter function
BindingSource	Source for the binding, including the type and value
BindingSpec	Specification of parameters for `@injectable()`
BindingTag	Binding tag can be a simple name or name/value pairs
BindingTemplate	A function as the template to configure bindings
BoundValue
ClassBindingSource	Binding source for `toClass`
ConstantBindingSource	Binding source for `to`
Constructor	A class constructor accepting arbitrary arguments.
ContextEvent	Events emitted by a context
ContextEventListener	Synchronous listener for context events
ContextEventObserver	Context event observer type - An instance of `ContextObserver` or a function
ContextEventType	Context event types. We support `bind` and `unbind` for now but keep it open for new types
ContextObserverFn	Listen on `bind`, `unbind`, or other events
DynamicValueBindingSource	Binding source for `toDynamicValue`
GenericInterceptor	An interceptor function to be invoked in a chain for the given context. It serves as the base interface for various types of interceptors, such as method invocation interceptor or request/response processing interceptor.
GenericInterceptorOrKey	Interceptor function or a binding key that resolves a generic interceptor function
Getter	The function injected by `@inject.getter(bindingSelector)`. It can be used to fetch bound value(s) from the underlying binding(s). The return value will be an array if the `bindingSelector` is a `BindingFilter` function.
InterceptorOrKey	Interceptor function or binding key that can be used as parameters for `@intercept()`
InvocationArgs	Array of arguments for a method invocation
InvocationOptions	Options to control invocations
InvocationResult	Return value for a method invocation
JSONPrimitive	JSON primitive types: - string - number - boolean - null
JSONValue	JSON values - primitive - object - array
MapObject
Next	The `next` function that can be used to invoke next generic interceptor in the chain
NonVoid	Any type except `void`. We use this type to enforce that interceptor functions always return a value (including undefined or null).
ProviderBindingSource	Binding source for `toProvider`
ResolutionAction	A function to be executed with the resolution session
ResolutionElement	Binding or injection elements tracked by resolution sessions
ResolutionOptionsOrSession	Resolution options or session
Setter	The function injected by `@inject.setter(bindingKey)`. It sets the underlying binding to a constant value using `binding.to(value)`.
TagMap
TypeNamespaceMapping	Mapping artifact types to binding key namespaces (prefixes).
ValueFactory	A factory function for `toDynamicValue`
ValueOrPromise	Representing a value or promise. This type is used to represent results of synchronous/asynchronous resolution of values. Note that we are using PromiseLike instead of native Promise to describe the asynchronous variant. This allows producers of async values to use any Promise implementation (e.g. Bluebird) instead of native Promises provided by JavaScript runtime.