KVO Binding sample

KVOBindingImplements.swift

/// 바인딩
private var observations: [NSKeyValueObservation] = []
private var viewModel = ExpenseViewModel()

// 뷰 바인딩
observations = [
    viewModel.observe(\.price) {
        let price = $0 ?? 0.0
        self.updatePriceText(with: price)
        self.changesPublisher.onNext(1)
    },
    viewModel.observe(\.title) { [tfTitle] in
        if tfTitle.isFirstResponder == false {
            tfTitle.text = $0
        }
        self.limitTitle($0)
        self.changesPublisher.onNext(1)
    },
    viewModel.observe(\.text) { [tvContents, placeHolder] in
        let text = $0 as? String
        if tvContents.isFirstResponder == false {
            tvContents.text = text
            placeHolder.isHidden = (text?.count ?? 0)  > 0
        }
    }
]