In my angular2 app i want to create a map which takes a number as key and returns an array of objects. I am currently implementing in following way but no luck. How should i implement it or should i use some other data structure for this purpose? I want to use map because maybe its fast?
Declaration
private myarray : [{productId : number , price : number , discount : number}];
priceListMap : Map<number, [{productId : number , price : number , discount : number}]>
= new Map<number, [{productId : number , price : number , discount : number}]>();
Usage
this.myarray.push({productId : 1 , price : 100 , discount : 10});
this.myarray.push({productId : 2 , price : 200 , discount : 20});
this.myarray.push({productId : 3 , price : 300 , discount : 30});
this.priceListMap.set(1 , this.myarray);
this.myarray = null;
this.myarray.push({productId : 1 , price : 400 , discount : 10});
this.myarray.push({productId : 2 , price : 500 , discount : 20});
this.myarray.push({productId : 3 , price : 600 , discount : 30});
this.priceListMap.set(2 , this.myarray);
this.myarray = null;
this.myarray.push({productId : 1 , price : 700 , discount : 10});
this.myarray.push({productId : 2 , price : 800 , discount : 20});
this.myarray.push({productId : 3 , price : 900 , discount : 30});
this.priceListMap.set(3 , this.myarray);
this.myarray = null;
I want to get an array of 3 objects if i use this.priceList.get(1);
This question is related to
arrays
json
angular
typescript
First thing, define a type or interface for your object, it will make things much more readable:
type Product = { productId: number; price: number; discount: number };
You used a tuple of size one instead of array, it should look like this:
let myarray: Product[];
let priceListMap : Map<number, Product[]> = new Map<number, Product[]>();
So now this works fine:
myarray.push({productId : 1 , price : 100 , discount : 10});
myarray.push({productId : 2 , price : 200 , discount : 20});
myarray.push({productId : 3 , price : 300 , discount : 30});
priceListMap.set(1 , this.myarray);
myarray = null;
The most simple way is to use Record type Record<number, productDetails >
interface productDetails {
productId : number ,
price : number ,
discount : number
};
const myVar : Record<number, productDetails> = {
1: {
productId : number ,
price : number ,
discount : number
}
}
you can also skip creating dictionary altogether. i used below approach to same problem .
mappedItems: {};
items.forEach(item => {
if (mappedItems[item.key]) {
mappedItems[item.key].push({productId : item.productId , price : item.price , discount : item.discount});
} else {
mappedItems[item.key] = [];
mappedItems[item.key].push({productId : item.productId , price : item.price , discount : item.discount}));
}
});
Source: Stackoverflow.com