210604 Fri

학습 내용: lazy var

A lazy stored property is a property whose initial value isn’t calculated until the first time it’s used.

Lazy properties are useful

1. when the initial value for a property is dependent on outside factors whose values aren’t known until after an instance’s initialization is complete.
2. when the initial value for a property requires complex or computationally expensive setup that shouldn’t be performed unless or until it’s needed.

• 예제 코드

  class DataImporter {
      /*
      DataImporter is a class to import data from an external file.
      The class is assumed to take a nontrivial amount of time to initialize.
      */
      var filename = "data.txt"
      // the DataImporter class would provide data importing functionality here
  }
  
  class DataManager {
      lazy var importer = DataImporter()
      var data = [String]()
      // the DataManager class would provide data management functionality here
  }
  
  let manager = DataManager()
  manager.data.append("Some data")
  manager.data.append("Some more data")
  // the DataImporter instance for the importer property hasn't yet been created
  
  print(manager.importer.filename)
  // the DataImporter instance for the importer property has now been created
  // Prints "data.txt"

문제점/고민한점 → 해결방안

• 베스트는 컬렉션뷰 하나를 쓰고 셀을 바꾸는 방법 (??)
• 컬렉션뷰 리스트 만드는 방법

방법 모르겠고

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