Class reflection¶

Creating an instance¶

To get started with reflection, create a ReflectionClass instance and pass a reference to a class constructor. You can also pass an instance of a class and the constructor will be inferred.

const reflect = new ReflectionClass(ExampleClass);
const reflect = new ReflectionClass(new ExampleClass());

Properties¶

name: string¶

The name of the class as a string.

parent: ReflectionClass?¶

The reflection instance for the parent class or undefined if the class has no parent.

target: Type<T>¶

A reference to the underlying class constructor.

prototype: Object¶

A reference to the underlying class prototype.

Retrieving methods¶

getMethods(filter?: MethodFilter)¶

Returns an array of ReflectionMethod instances that describe each method on the class.

Parameters

Name	Type	Description	Default
filter	MethodFilter, undefined	An optional filter to choose what kind of methods are returned.	undefined

Examples

// Iterate over all methods
for (const method of reflect.getMethods()) {}

// Filter static methods
const staticMethods = reflect.getMethods(MethodFilter.Static);

// Multiple filters (AND)
const staticOwnMethods = reflect.getMethods(
    MethodFilter.Static | MethodFilter.Own
);

getMethod(name: string, filter?: MethodFilter)¶

Returns the ReflectionMethod instance for a method matching the given name. Returns undefined when no matching method is found.

Parameters

Name	Type	Description	Default
name	string	The name of the method to search for.	required
filter	MethodFilter, undefined	An optional filter to choose what kind of methods are checked.	undefined

Examples

const method = reflect.getMethod('methodName');
method?.invoke(o);

hasMethod(name: string, filter?: MethodFilter)¶

Returns true if the class has a method matching the given name.

Parameters

Name	Type	Description	Default
name	string	The name of the method to search for.	required
filter	MethodFilter, undefined	An optional filter to use when checking for a matching method.	undefined

Examples

reflect.hasMethod('staticMethodName') // true
reflect.hasMethod('staticMethodName', MethodFilter.Local) // false

getConstructorMethod()¶

Returns a ReflectionMethod instance representing the constructor method for the class. The constructor method is guaranteed to exist, even if one is not explicitly defined.

Examples

// These return the same exact object
reflect.getConstructorMethod();
reflect.getMethod('constructor');

Retrieving properties¶

getProperties(filter?: PropertyFilter)¶

Returns an array of ReflectionProperty instances that describe each known property on the class.

Parameters

Name	Type	Description	Default
filter	PropertyFilter, undefined	An optional filter to choose what kind of properties are returned.	undefined

Examples

// Iterate over all properties
for (const property of reflect.getProperties()) {}

// Filter own properties (not from a parent class)
const ownProperties = reflect.getProperties(PropertyFilter.Own);

getProperty(name: string, filter?: PropertyFilter)¶

Returns the ReflectionProperty instance for a property matching the given name. Returns undefined when no matching property is found.

Parameters

Name	Type	Description	Default
name	string	The name of the property to search for.	required
filter	PropertyFilter, undefined	An optional filter to choose what kind of properties are checked.	undefined

Examples

const property = reflect.getProperty('propertyName');
const value = property?.getMetadata('key');

hasProperty(name: string, filter?: PropertyFilter)¶

Returns true if the class has a property matching the given name.

Parameters

Name	Type	Description	Default
name	string	The name of the property to search for.	required
filter	PropertyFilter, undefined	An optional filter to use when checking for a matching property.	undefined

Examples

reflect.hasProperty('propertyName')

Retrieving attributes¶

This library has a powerful alternative to decorators called attributes. You can use the following methods to retrieve attribute instances that have been applied to a class.

getAttributes(attribute?: IAttribute<any>)¶

Returns an array of instances of the specified attribute on the class. When the attribute argument is not supplied, it will return all attributes on the class.

Parameters

Name	Type	Description	Default
attribute	IAttribute<any>	A reference to the attribute function.	undefined

Examples

for (const attribute of reflect.getAttributes(ExampleAttribute)) {
    // Do something
}

getAttribute(attribute: IAttribute<any>)¶

Returns an instance of the specified attribute on the class or undefined if not found. Only the last instance (the instance declared in the code last) will be returned.

Parameters

Name	Type	Description	Default
attribute	IAttribute<any>	A reference to the attribute function.	required

Examples

const latest = reflect.getAttributes(ExampleAttribute);

hasAttribute(attribute: IAttribute<any>)¶

Returns true if the class has any attributes of the specified type applied.

Parameters

Name	Type	Description	Default
attribute	IAttribute<any>	A reference to the attribute function.	required

Examples

if (reflect.hasAttribute(ExampleAttribute)) {
    // Do something!
}

Managing metadata¶

These methods use the reflect-metadata library under the hood. You can use the @Meta decorator built into this package, or refer to the TypeScript Handbook on Decorators, to set metadata on your classes.

getMetadata(key: any)¶

Returns the value of a metadata key on the class.

Parameters

Name	Type	Description	Default
key	any	The key to look for. This must be identical to the key you originally used to store the data.	required

getAllMetadata()¶

Returns a Map containing all metadata on the class.

Examples

const meta = reflect.getAllMetadata();
const value = meta.get('key');

setMetadata(key: any, value: any)¶

Sets the value of a metadata key on the class.

Parameters

Name	Type	Description	Default
key	any	The key to set data for.	required
value	any	The data to store under the key. Existing data will be overwritten.	required

hasMetadata(key: any)¶

Returns true if this class has metadata matching the given key.

Parameters

Name	Type	Description	Default
key	any	The key to look for. This must be identical to the key you originally used to store the data.	required

Ancestry¶

getHierarchy()¶

Returns an array of ReflectionClass instances representing the hierarchy of the current class. The first element in the array will be the topmost parent class, and the last element will be the current class.

For classes with no parents, this will return an array containing only the current class.

Examples

class Vehicle {}
class Car extends Vehicle {}
class Hatchback extends Car {}

const reflection = new ReflectionClass(Hatchback);
const hierarchy = reflection.getHierachy();

The above hierarchy variable will be an array that looks like the following.

[
    ReflectionClass(Vehicle),
    ReflectionClass(Car),
    ReflectionClass(Hatchback)
]

hasType(type: Type<any>)¶

Returns true if this class has a class within its hierarchy, including itself, which matches the given class constructor type.

Parameters

Name	Type	Description	Default
type	Type<any>	A reference to the class to check against.	required

Examples

class Vehicle {}
class Car extends Vehicle {}
class Hatchback extends Car {}

const reflection = new ReflectionClass(Hatchback);

reflection.hasType(Car) // true
reflection.hasType(Vehicle) // true
reflection.hasType(Hatchback) // true - includes itself

hasAncestorType(type: Type<any>)¶

Returns true if this class has a class within its hierarchy, not including itself, which matches the given class constructor type.

Parameters

Name	Type	Description	Default
type	Type<any>	A reference to the class to check against.	required

Examples

class Vehicle {}
class Car extends Vehicle {}
class Hatchback extends Car {}

const reflection = new ReflectionClass(Hatchback);

reflection.hasAncestorType(Car) // true
reflection.hasAncestorType(Vehicle) // true
reflection.hasAncestorType(Hatchback) // false - doesn't include itself

Creating instances¶

create(args?: any[])¶

Creates a new instance of the class with the given constructor arguments.

Parameters

Name	Type	Description	Default
args	any[]	An array of constructor arguments.	[]

Examples

class Hatchback {
    public constructor(public name: string, public year: number) {

    }
}

const reflection = new ReflectionClass(Hatchback);
const instance = reflection.create(['Honda Civic', 2020]);