tinspector
An introspection (reflection) library, extract JavaScript/TypeScript type into metadata information such as class name, methods, parameters and their appropriate data types
Example
Result of metadata
variable above is like below
kind: 'Class' name: 'MyAwesomeClass' type: MyAwesomeClass decorators: properties: ctor: kind: 'Constructor' name: 'constructor' parameters: methods: kind: 'Method' name: 'myAwesomeMethod' parameters: kind: 'Parameter' name: 'stringPar' type: String decorators: properties: {} kind: 'Parameter' name: 'numberPar' type: Number decorators: properties: {} decorators: cache: '20s' returnType: Number kind: 'Method' name: 'awesome' parameters: decorators: returnType: undefined
Features
- Inspect function
- Inspect module or file
- Inspect class
- Inspect class with inheritance
- Inspect getter and setter
- Inspect methods
- Inspect parameters
- Supported inspect destructured parameter
- Supported inspect rest parameter
- Supported inspect parameter with complex default value
- x Inspect decorators
- x Inspect parameter properties
- x Inspect type information
- x Configurable decorator (inheritable / allow multiple)
- x Generic class inheritance
TypeScript Requirement
To be able to inspect type information its required to enable configuration below in tsconfig.json
Inspect Type Information
TypeScript when emitDecoratorMetadata
enabled, TypeScript will add type information during compile time. This make it possible to extract typescript type information during runtime.
CAVEAT
TypeScript
emitDecoratorMetadata
has some limitation.
- Declaration should have at least one decorator to get metadata (type information)
- Array element type information not included.
- Generic type information not included.
Based on limitation above its required at least have one decorator to make tinspector to be able to extract type information:
tinspector will be able to get type information of the method's return type and parameters of the awesome
method above. Note that we applied @reflect.noop()
decorator on the awesome
method. @reflect.noop()
does nothing except to force TypeScript to emit metadata information.
Above code showing that we able to get type information of a property.
Above code showing that we able to get type information of parameters of the constructor, by applying decorator on the class level.
Inspect Array and Generic Type
To get type information of an Array and Generic type its required to use @reflect.type()
decorator and provide the type on the callback parameter.
Above code showing that we able to get method's return type information by providing @reflect.type([Number])
. Note that the [Number]
is an array of Number
.
We will be able to get generic type information such as Partial
, Required
etc by applying @reflect.type()
like above.
If you receive
ReferenceError: <type name> is not defined
error, thats mean you use@reflect.type(MyType)
prior than its declaration. To solve this issue you can use callback@reflect.type(x => MyType)
or@reflect.type(x => [MyType])
for array type.
Inspect Generic Class Information
With above trick its possible to get generic type information in a generic class members with some extra configuration below
Above code showing that we add a specialized decorator @generic.template()
to define generic template type. We also defined data type of the generic parameters using @reflect.type()
decorator. Next on the inherited class we specify @generic.type()
to define types replace the generic template. Note that the order of the parameter on @generic.template()
and @generic.type()
is important.
Inspect Parameter Properties
TypeScript has parameter properties feature, which make it possible to use constructor parameter as property. tinspector able to extract parameter properties type information by using @reflect.parameterProperties()
decorator.
Custom Decorator
Tinspector able to extract classes/methods/properties/parameters decorated with predefined decorators. There are predefined decorators should be use to be able for Tinspector to inspect the decorators
Decorator | Description |
---|---|
decorateClass |
Decorate class with object specified in parameter |
decorateProperty |
Decorate property with object specified in parameter |
decorateMethod |
Decorate method with object specified in parameter |
decorateParameter |
Decorate parameter with object specified in parameter |
decorate |
Decorate any (class, property, method, parameter) with object specified in parameter |
mergeDecorator |
Merge multiple decorators into one, useful on creating custom decorator |
Example usage
Parameter passed on each decorator can be any object contains value, methods etc, those value will be returned when the class metadata extracted.
Create your own custom decorator by creating function returns decorator above
// create custom decorator
Use mergeDecorator
to combine multiple decorator on custom decorator
// create custom decorator
Decorator Option (Inheritance, Allow Multiple)
Decorator can be further configured to match the behavior you need like below.
decorateMethoddata, option
Option is a simple object with properties:
inherit
Boolean
Iffalse
decorator will not be merged on the derived class. Defaulttrue
allowMultiple
Boolean
Iffalse
throw error when multiple decorator applied on class. Also when setfalse
will prevent super class decorator being merged into derived class when already exists. When setfalse
, decorator required to haveDecoratorId
property to identify the similar decorator.
Example disable decorator inheritance
// { log: true} will not inherited on this class
Example disable multiple decorator on inheritance
// parent decorator will not merged// guaranteed derived class only have single decorator with specific ID
Flush Cache
By default reflect process cached globally for performance reason. But in some case if you modify the class preferences by adding a new decorator etc, your new update will not returned until you flush the cache.