pip-services3-commons-nodex/src/reflect/PropertyReflector.ts

Portable abstractions and patterns for Pip.Services in Node.js / ES2017

/** @module reflect */

/**
 * Helper class to perform property introspection and dynamic reading and writing.
 * 
 * This class has symmetric implementation across all languages supported
 * by Pip.Services toolkit and used to support dynamic data processing.
 * 
 * Because all languages have different casing and case sensitivity rules,
 * this PropertyReflector treats all property names as case insensitive.
 * 
 * ### Example ###
 * 
 *     let myObj = new MyObject();
 *     
 *     let properties = PropertyReflector.getPropertyNames();
 *     PropertyReflector.hasProperty(myObj, "myProperty");
 *     let value = PropertyReflector.getProperty(myObj, "myProperty");
 *     PropertyReflector.setProperty(myObj, "myProperty", 123);
 */
export class PropertyReflector {
	private static matchField(fieldName: string, fieldValue: any, expectedName: string): boolean {
        if (typeof fieldValue === "function") return false;
        if (fieldName.startsWith('_')) return false;
        if (expectedName == null) return true;
        return fieldName.toLowerCase() == expectedName;
	}

	/**
	 * Checks if object has a property with specified name..
	 * 
	 * @param obj 	an object to introspect.
	 * @param name 	a name of the property to check.
	 * @returns true if the object has the property and false if it doesn't.
	 */
	public static hasProperty(obj: any, name: string): boolean {
		if (obj == null) {
			throw new Error("Object cannot be null");
		}
		if (name == null) {
			throw new Error("Property name cannot be null");
		}
		
        name = name.toLowerCase();
        for (let field in obj) {
            let fieldValue = obj[field];
        	if (PropertyReflector.matchField(field, fieldValue, name)) {
        		return true;
			}
        }
		
        return false;
	}

	/**
	 * Gets value of object property specified by its name.
	 * 
	 * @param obj 	an object to read property from.
	 * @param name 	a name of the property to get.
	 * @returns the property value or null if property doesn't exist or introspection failed.
	 */
	public static getProperty(obj: any, name: string): any {
		if (obj == null) {
			throw new Error("Object cannot be null");
		}
		if (name == null) {
			throw new Error("Property name cannot be null");
		}

		name = name.toLowerCase()

		let fields: string[] = this.getAllFieldsOfObject(obj)
		
		for (let index = 0; index < fields.length; index++) {
            let fieldValue = obj[fields[index]];
        	try {
	        	if (PropertyReflector.matchField(fields[index], fieldValue, name)) {
	        		return fieldValue;
				}
        	} catch (ex) {
        		// Ignore exceptions
			}
        }
		
        return null;
	}

	private static getAllFieldsOfObject(obj: any):string[] {
		let properties: string[] = [];
		
		while (obj != null && Object.getPrototypeOf(obj) != null) {
			// enumerable props
			for (let prop in obj) {
				properties.push(prop.toString())
			}

			// non-enumerable props
			Object.entries(Object.getOwnPropertyDescriptors(obj.constructor.prototype)).forEach(prop=> {
				if (prop[1].get != undefined || prop[1].set != undefined){
					properties.push(prop[0])
				}
			})
			
			obj = Object.getPrototypeOf(obj)
		}

		return properties
	}
	
	/**
     * Gets names of all properties implemented in specified object.
     * 
     * @param obj   an objec to introspect.
     * @returns a list with property names.
     */
	public static getPropertyNames(obj: any): string[] {
        let properties: string[] = [];
		let fields: string[] = this.getAllFieldsOfObject(obj)
		
		for (let index = 0; index < fields.length; index++) {
            let fieldValue = obj[fields[index]];
        	if (PropertyReflector.matchField(fields[index], fieldValue, null)) {
        		properties.push(fields[index]);
			}
        }
		        
		return properties;
	}

	/**
     * Get values of all properties in specified object
	 * and returns them as a map.
     * 
     * @param obj   an object to get properties from.
     * @returns a map, containing the names of the object's properties and their values.
     */
	public static getProperties(obj: any): any {
        let map: any = {};
		
		let fields: string[] = this.getAllFieldsOfObject(obj)
		
		for (let index = 0; index < fields.length; index++) {
            let fieldValue = obj[fields[index]];
        	try {
	        	if (PropertyReflector.matchField(fields[index], fieldValue, null)) {
	        		map[fields[index]] = fieldValue;
				}
        	} catch (ex) {
        		// Ignore exception
        	}
        }
		        
		return map;
	}
	
	/**
	 * Sets value of object property specified by its name.
	 * 
	 * If the property does not exist or introspection fails
	 * this method doesn't do anything and doesn't any throw errors.
	 * 
	 * @param obj 	an object to write property to.
	 * @param name 	a name of the property to set.
	 * @param value a new value for the property to set.
     */
	public static setProperty(obj: any, name: string, value: any): void {
		if (obj == null) {
			throw new Error("Object cannot be null");
		}
		if (name == null) {
			throw new Error("Property name cannot be null");
		}

        let expectedName = name.toLowerCase();
        let fields: string[] = this.getAllFieldsOfObject(obj)
		
		for (let index = 0; index < fields.length; index++) {
            let fieldValue = obj[fields[index]];
	    	try {        		
	            if (PropertyReflector.matchField(fields[index], fieldValue, expectedName)) { 
	        		obj[fields[index]] = value;
	        		return;
	            }
	    	} catch (ex) {
	    		// Ignore exception
	    	}
        }

        // If no existing properties found set it directly
        obj[name] = value;
	}
	
	/**
	 * Sets values of some (all) object properties.
	 * 
	 * If some properties do not exist or introspection fails
	 * they are just silently skipped and no errors thrown.
	 * 
	 * @param obj 		 an object to write properties to.
	 * @param values 	a map, containing property names and their values.
	 * 
	 * @see [[setProperty]]
	 */
	public static setProperties(obj: any, values: any): void {
		if (values == null) return;
		
		for (let field in values) {
            let fieldValue = values[field];
			PropertyReflector.setProperty(obj, field, fieldValue);
		}
	}
}