So far we’ve just been hitting the API anytime we need to display some day. Let’s create a Core Data model that will let us cache the JSON payload.



We’re hitting the API every time we need some data.


  1. Create a new file of type Data Model
  2. Add an Entity named NASA
  3. Add an attribute for each property from Pod.swift
  • date: Date?
  • url: URI?
  • hdurl: URI?
  • thumbnailUrl: URI?
  • title: String?
  • copyright: String?
  • explanation: String?
  • mediaType: String?
  • serviceVersion: String?


<model type="" documentVersion="1.0" lastSavedToolsVersion="19574" systemVersion="21A559" minimumToolsVersion="Automatic" sourceLanguage="Swift" userDefinedModelVersionIdentifier="">
<entity name="NASA" representedClassName="NASA" syncable="YES" codeGenerationType="class">
    <attribute name="copyright" optional="YES" attributeType="String"/>
    <attribute name="date" optional="YES" attributeType="Date" usesScalarValueType="NO"/>
    <attribute name="explanation" optional="YES" attributeType="String"/>
    <attribute name="hdurl" optional="YES" attributeType="URI"/>
    <attribute name="mediaType" optional="YES" attributeType="String"/>
    <attribute name="serviceVersion" optional="YES" attributeType="String"/>
    <attribute name="thumbnailUrl" optional="YES" attributeType="URI"/>
    <attribute name="title" optional="YES" attributeType="String"/>
    <attribute name="url" optional="YES" attributeType="URI"/>