Fahad salamat randhawa

step20c_constructor/app.ts

@@ -25,11 +25,14 @@ let d: B = new B("C"); // Thsi is also not working
 // If parent class does not provide constructor and child class provide constrcutor then 
 // child class must call super() within child's class constructor
 // call to super can be at any line in constructor unlike any other object oriented language with call to super must be as first line
+//* Correction to above line, call to super must be on first line in the child constructor, otherwise you will get a warning while using "this" before super *//
 class C {
+
 }
 class D extends C {
  name:string;
  constructor(theName: string,age:number) {
+ //Super() //must be here
  this.name = theName; 
  console.log("D constrcutor");
  super(); // 
@@ -38,6 +41,7 @@ class D extends C {
 let aa: C = new C(); // This is working as expected
 let bb: D = new D(); // This is not working because child class has its 2 argumnet constrcutor
 let cc: D = new D("C",8); // This is working as expected
+let dc: D = new C(); //class C must have atleast all properties of class D to be assigned to type D
 
 
 // Case c:
@@ -57,6 +61,7 @@ class E {
 class F extends E {
  name:string;
  constructor(theName: string) {
+ //must call super here
  this.name = theName; 
  console.log("F constrcutor");
  super(theName,4); // Must call super with two arguments

step26_interfaces/app.ts

@@ -19,10 +19,11 @@ printLabel({mylabel: "Size 10 Object"});//Case 2a missing or renamed property: E
 
 //Case 2b
 //A type can include an index signature to explicitly indicate that excess properties are permitted in with fresh objects:
-function printLabelX(labelledObj: {[x: string]:any}) {////Note now 'x' can have any name, just that the property should be of type string
+function printLabelX(labelledObj: {[x: string]:any}) {////Note now 'x' can have any name, just that the property name should be of type string
  console.log(arguments[0]);
 }
-printLabelX({name: "Zia"});// Ok, `name` matched by index signature
+printLabelX({name: "Zia Khan"});// Ok, `name` matched by index signature name: any
+printLabelX({value: 2});// Ok, `value` matched by index signature value: any
 
 
 //Case 3
@@ -33,7 +34,7 @@ printLabel({size: 10, label: "Size 10 Object"});//Case 3 Fresh Literal: Error no
 
 
 //Stale Objects:
-
+// function decleration at the top
 //Case 1:
 var myObj1 = {label: "Size 10 Object"};
 printLabel(myObj1);//Case 1 exact properties: OK
@@ -86,7 +87,7 @@ printLabelY2({name: "Zia"});// Ok, `name` matched by index signature
 
 //Case 3
 printLabelY({size: 11, label: "Size 11 Object"});//Case 3 Fresh Literal: Error no extra properties allowed
-
+printLabelY2({size: 11, label: "Size 11 Object"})//Case 3 extra properties allowed as Fresh Literal due to index signature
 
 
 

step36c_reflection/app.ts

@@ -6,7 +6,7 @@
 
 import "reflect-metadata";
 
-function logType(target : any, key : string) {
+function logType(target : any, key : string) { //targe=Demo{} key=attr1
  var t = Reflect.getMetadata("design:type", target, key);
  console.log(`${key} type: ${t.name}`);
  }