pip-services3-commons-node/src/reflect/ObjectReader.ts

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

/** @module reflect */
/** @hidden */ 
let _ = require('lodash');

import { PropertyReflector } from './PropertyReflector';
import { IntegerConverter } from '../convert/IntegerConverter';

/**
 * Helper class to perform property introspection and dynamic reading.
 * 
 * In contrast to [[PropertyReflector]] which only introspects regular objects,
 * this ObjectReader is also able to handle maps and arrays.
 * For maps properties are key-pairs identified by string keys,
 * For arrays properties are elements identified by integer index.
 * 
 * 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 ObjectReader treats all property names as case insensitive.
 *
 * @see [[PropertyReflector]]
 * 
 * ### Example ###
 * 
 *     let myObj = new MyObject();
 *     
 *     let properties = ObjectReader.getPropertyNames();
 *     ObjectReader.hasProperty(myObj, "myProperty");
 *     let value = PropertyReflector.getProperty(myObj, "myProperty");
 *     
 *     let myMap = { key1: 123, key2: "ABC" };
 *     ObjectReader.hasProperty(myMap, "key1");
 *     let value = ObjectReader.getProperty(myMap, "key1");
 *     
 *     let myArray = [1, 2, 3]
 *     ObjectReader.hasProperty(myArrat, "0");
 *     let value = ObjectReader.getProperty(myArray, "0");
 */
export class ObjectReader {
    
    /**
     * Gets a real object value.
     * If object is a wrapper, it unwraps the value behind it. 
     * Otherwise it returns the same object value.
     * 
     * @param obj   an object to unwrap..
     * @returns an actual (unwrapped) object value. 
     */
    public static getValue(obj: any): any {
    	// Todo: just a blank implementation for compatibility
        return obj;
    }

    /**
	 * Checks if object has a property with specified name.
     * 
     * The object can be a user defined object, map or array.
     * The property name correspondently must be object property,
     * map key or array index.
	 * 
	 * @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 || name == null) {
        	return false;
        } else if (_.isObject(obj) && !_.isDate(obj)) {
            return PropertyReflector.hasProperty(obj, name);
        } else if (_.isArray(obj)) {
            let index = IntegerConverter.toNullableInteger(name);
            return index != null && index < obj.length;
        } else {
            return false;
        }
    }

    /**
	 * Gets value of object property specified by its name.
	 * 
     * The object can be a user defined object, map or array.
     * The property name correspondently must be object property,
     * map key or array index.
     * 
	 * @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 || name == null) {
        	return null;
        } else if (_.isObject(obj) && !_.isDate(obj)) {
            return PropertyReflector.getProperty(obj, name);
        } else if (_.isArray(obj)) {
            let index = IntegerConverter.toNullableInteger(name);
            return index != null && index < obj.length ? obj[index] : null;
        } else {
            return null;
        }
    }

    /**
     * Gets names of all properties implemented in specified object.
     * 
     * The object can be a user defined object, map or array.
     * Returned property name correspondently are object properties,
     * map keys or array indexes.
     * 
     * @param obj   an objec to introspect.
     * @returns a list with property names.
     */
	public static getPropertyNames(obj: any): string[] {
        let properties: string[] = [];
        
        if (obj == null) {
        	// Do nothing
        } else if (_.isObject(obj) && !_.isDate(obj)) {
            properties = PropertyReflector.getPropertyNames(obj);
        } else if (_.isArray(obj)) {
			let length = obj.length;
            for (let index = 0; index < length; index++)
            	properties.push(index.toString());
        } else {
            // Do nothing
        }

        return properties;
    }

    /**
     * Get values of all properties in specified object
	 * and returns them as a map.
     * 
     * The object can be a user defined object, map or array.
     * Returned properties correspondently are object properties,
     * map key-pairs or array elements with their indexes.
     * 
     * @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 = {};
        
        if (obj == null) {
        	// Do nothing
        } else if (_.isObject(obj) && !_.isDate(obj)) {
            map = PropertyReflector.getProperties(obj);
        } else if (_.isArray(obj)) {
			let length = obj.length;
            for (let index = 0; index < length; index++)
                map[index.toString()] = obj[index];
        } else {
            // Do nothing
        }

        return map;
    }
}