notes

React.note vs useMemo2020. 7. 10.

`React.memo`

Higher order component.
prop change만을 체크함. 감싼 컴포넌트 안에 useState, useContext등이 있다면, 역시 해당 state 변경에 따라 rerender됨.

`useMemo`

Hook.
deps array에 포함된 deps가 변경되지 않으면 memoized value를 반환하는 함수.

react

flex2020. 7. 9.

`flex`

flex-grow, flex-shrink, + flex-basis의 shorthand이다.

syntax

One-value syntax: the value must be one of:
- a <number>: In this case it is interpreted as flex: <number> 1 0; the <flex-shrink> value is assumed to be 1 and the <flex-basis> value is assumed to be 0.
- one of the keywords: none, auto, or initial.
Two-value syntax: the first value must be a <number> and it is interpreted as <flex-grow>. The second value must be one of:
- a <number>: then it is interpreted as <flex-shrink>.
- a valid value for width: then it is interpreted as <flex-basis>.
Three-value syntax: the values must be in the following order:
- a <number> for <flex-grow>.
- a <number> for <flex-shrink>.
- a valid value for width for <flex-basis>.

css flexbox

String interpolation produces a debug description for an optional value; did you mean to make this explicit?2020. 7. 8.

Screen Shot 2020-07-08 at 23 06 18

default:
-   fatalError("Unexpected Segue identifier; \(segue.identifier)")
+   fatalError("Unexpected Segue identifier; \(String(describing: segue.identifier))")

default:
-   fatalError("Unexpected Segue identifier; \(segue.identifier)")
+   fatalError("Unexpected Segue identifier; \(String(describing: segue.identifier))")

swift iOS deprecated

Delegation Pattern2020. 7. 6.

https://en.wikipedia.org/wiki/Delegation_pattern

class Rectangle(val width: Int, val height: Int) {
    fun area() = width * height
}

class Window(val bounds: Rectangle) {
    // Delegation
    fun  area() = bounds.area()
}

class Rectangle(val width: Int, val height: Int) {
    fun area() = width * height
}

class Window(val bounds: Rectangle) {
    // Delegation
    fun  area() = bounds.area()
}

Links

oop

sourceViewController -> source2020. 7. 6.

Implement Navigation을 진행하다가 아래 워닝을 만났다.

Screen Shot 2020-07-07 at 6 32 27

    //MARK: Actions
    @IBAction func unwindToMealList(sender: UIStoryboardSegue) {
-        if let sourceViewContoller = sender.sourceViewController as? MealViewController, let meal = sourceViewContoller.meal {
+        if let sourceViewContoller = sender.source as? MealViewController, let meal = sourceViewContoller.meal {
            // Add new meal.
            let newIndexPath = IndexPath(row: meals.count, section: 0)
            meals.append(meal)
            tableView.insertRows(at: [newIndexPath], with: .automatic)
        }
    }

    //MARK: Actions
    @IBAction func unwindToMealList(sender: UIStoryboardSegue) {
-        if let sourceViewContoller = sender.sourceViewController as? MealViewController, let meal = sourceViewContoller.meal {
+        if let sourceViewContoller = sender.source as? MealViewController, let meal = sourceViewContoller.meal {
            // Add new meal.
            let newIndexPath = IndexPath(row: meals.count, section: 0)
            meals.append(meal)
            tableView.insertRows(at: [newIndexPath], with: .automatic)
        }
    }