Method reflection¶

Retrieving an instance¶

Retrieve an instance from the parent class using getMethod() or getMethods(). It is not possible to manually instantiate a reflection method.

Properties¶

name: string¶

The name of the method as a string.

class: ReflectionClass¶

The class that this method belongs to.

isConstructor: boolean¶

Whether or not the method is the constructor for the class.

isStatic: boolean¶

Whether or not the method is static.

isTyped: boolean¶

Whether or not the method has type metadata available from TypeScript.

prototype: Object¶

A reference to the underlying class prototype.

target: Function¶

A reference to the method's function on the class prototype.

Invoking methods¶

getClosure(object?: T | null)¶

Returns an anonymous function that invokes the method on the given object.

Parameters

Name	Type	Description	Default
object	T, null, undefined	An instance of the class to invoke the method on. For static methods, pass null or undefined.	undefined

Examples

const fn = method.getClosure(instance);
fn(...args);

invoke(object?: T | null, ...args: any[])¶

Invokes the method on the given object with optional arguments.

Parameters

Name	Type	Description	Default
object	T, null, undefined	An instance of the class to invoke the method on. For static methods, pass null or undefined.	undefined
...args	any[]	Optional arguments to pass to the method.

Examples

method.invoke(instance);

method.invoke(instance, 'Arguments here!', true);

method.invoke(null, 'Static methods');

Managing parameters¶

getParameters(filter?: ParameterFilter)¶

Returns an array of ReflectionParameter instances which describe each parameter from the method.

Parameters

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

Examples

// Iterate over all parameters
for (const param of reflect.getParameters()) {}

// Filter parameters that don't have default values
const requiredParams = reflect.getParameters(
    ParameterFilter.WithoutDefault
);

// Multiple filters (AND)
// This will find all parameters with a non-generic type that have metadata
const knownNonPrimitives = reflect.getMethods(
    ParameterFilter.Meta | ParameterFilter.NonPrimitiveType
);

getParameter(name: string, filter?: ParameterFilter)¶

Returns a ReflectionParameter instance for the specified parameter. Returns undefined if there is no matching parameter.

Parameters

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

Examples

const param = method.getParameter('paramName');

getParameter(index: number)¶

Returns a ReflectionParameter instance for the parameter at the specified index. Returns undefined if there is no matching parameter.

Parameters

Name	Type	Description	Default
index	number	The index to retrieve (zero-based).	required

Examples

const param = method.getParameter(0);

hasParameter(name: string, filter?: ParameterFilter)¶

Returns true if the method contains a parameter with the specified name, optionally with a filter applied.

Parameters

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

Examples

if (method.hasParameter('paramName')) {
    // ...
}

Return types¶

getReturnType()¶

Returns the method's return type as it was defined by the TypeScript compiler. When type information is not available, or when the method does not return anything, undefined will be returned instead.

• When a function can return multiple types, this will return a generic Object
• When a function returns a class instance, this will return the class constructor

Examples

if (method.getReturnType() === String) {
    const str = method.invoke(o);
}

getReturnTypeString()¶

Returns the method's return type as a string. This will be identical to what the typeof operator would produce.

Examples

if (method.getReturnTypeString() === 'string') {
    const str = method.invoke(o);
}

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 method.

getAttributes(attribute?: IAttribute<any>)¶

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

Parameters

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

Examples

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

getAttribute(attribute: IAttribute<any>)¶

Returns an instance of the specified attribute on the method 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 = method.getAttributes(ExampleAttribute);

hasAttribute(attribute: IAttribute<any>)¶

Returns true if the method 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 (method.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 methods.

getMetadata(key: any)¶

Returns the value of a metadata key on the method.

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 method.

Examples

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

setMetadata(key: any, value: any)¶

Sets the value of a metadata key on the method.

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 method 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