Property reflection¶

Retrieving an instance¶

Retrieve an instance from the parent class using getProperty() or getProperties(). It is not possible to manually instantiate a reflection property.

Properties¶

name: string¶

The name of the property as a string.

class: ReflectionClass¶

The class that this property belongs to.

isTyped: boolean¶

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

Property type¶

getType()¶

Returns the property's expected type as it was defined by the TypeScript compiler. When type information is not available, or when the property does not define a type, undefined will be returned instead.

• When a property accepts multiple types, this will return a generic Object
• When a property accepts a class instance, this will return the class constructor

Examples

if (property.getType() === String) {}
if (property.getType() === undefined) {}

getTypeString()¶

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

Examples

if (property.getTypeString() === 'string') {}
if (property.getTypeString() === 'undefined') {}

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 property.

getAttributes(attribute?: IAttribute<any>)¶

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

Parameters

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

Examples

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

getAttribute(attribute: IAttribute<any>)¶

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

hasAttribute(attribute: IAttribute<any>)¶

Returns true if the property 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 (property.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 properties.

getMetadata(key: any)¶

Returns the value of a metadata key on the property.

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 property.

Examples

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

setMetadata(key: any, value: any)¶

Sets the value of a metadata key on the property.

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 property 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