Tableview need to be reloaded twice to update the data from textfield? - ios

Question

I have question about the tableView.
Here is my tableView code
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return tierCount
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cellIdentifier = "InterestRateTableViewCell"
guard let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifier, for: indexPath) as? InterestRateTableViewCell else {
fatalError("The dequed cell is not an instance of InterestRateTableViewCell.")
}
cell.interestRateTextField.delegate = self
cell.rowLabel.text = "\(indexPath.row + 1)."
if let interestText = cell.interestRateTextField.text {
if let interest = Double(interestText){
interestRateArray[indexPath.row] = interest
} else {
interestRateArray[indexPath.row] = nil
}
} else {
interestRateArray[indexPath.row] = nil
}
return cell
}
As you can see, I have the cellForRowAt method to get the value from the textfields in the cell, and assign to my arrays. (I actually have 2 textfields per cell.)
Basically, I let the users input and edit the textfield until they are happy then click this calculate button, which will call the calculation method. In the calculation method I call the "tableView.reloadData()" first to gather data from the textfields before proceed with the actual calculation.
The problem was when I ran the app. I typed values in all the textfields then clicked "calculate", but it showed error like the textfields were still empty. I clicked again, and it worked. It's like I had to reload twice to get things going.
Can anyone help me out?
By the way, please excuse my English. I'm not from the country that speak English.
edited: It may be useful to post the calculate button code here as someone suggested. So, here is the code of calculate button
#IBAction func calculateRepayment(_ sender: UIButton) {
//Reload data to get the lastest interest rate and duration values
DispatchQueue.main.async {
self.interestRateTableView.reloadData()
}
//Get the loan value from the text field
if let loanText = loanTextField.text {
if let loanValue = Double(loanText) {
loan = loanValue
} else {
print("Can not convert loan value to type Double.")
return
}
} else {
print("Loan value is nil")
return
}
tiers = []
var index = 0
var tier: Tier
for _ in 0..<tierCount {
if let interestRateValue = interestRateArray[index] {
if let durationValue = durationArrayInMonth[index] {
tier = Tier(interestRateInYear: interestRateValue, tierInMonth: durationValue)
tiers.append(tier)
index += 1
} else {
print("Duration array contain nil")
return
}
} else {
print("Interest rate array contain nil")
return
}
}
let calculator = Calculator()
repayment = calculator.calculateRepayment(tiers: tiers, loan: loan!)
if let repaymentValue = repayment {
repaymentLabel.text = "\(repaymentValue)"
totalRepaymentLabel.text = "\(repaymentValue * Double(termInYear!) * 12)"
} else {
repaymentLabel.text = "Error Calculating"
totalRepaymentLabel.text = ""
}
}

Answer 1

cellForRowAt is used for initially creating and configuring each cell, so the textfields are empty when this method is called.
UITableView.reloadData() documentation:
// Reloads everything from scratch. Redisplays visible rows. Note that this will cause any existing drop placeholder rows to be removed.
open func reloadData()
As it says in Apple's comment above, UITableView.reloadData() will reload everything from scratch. That includes your text fields.
There are a number of ways to fix your issue, but it's hard to say the best way without more context. Here's an example that would fit the current context of your code fairly closely:
class MyCustomTableViewCell: UITableViewCell {
#IBOutlet weak var interestRateTextField: UITextField!
var interestRateChangedHandler: (() -> ()) = nil
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
interestRateTextField.addTarget(self, action: #selector(interestRateChanged), for: UIControlEvents.editingChanged)
}
#objc
func interestRateChanged() {
interestRateChangedHandler?()
}
}
and cellForRowAtIndex:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cellIdentifier = "InterestRateTableViewCell"
guard let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifier, for: indexPath) as? InterestRateTableViewCell else {
fatalError("The dequed cell is not an instance of InterestRateTableViewCell.")
}
cell.rowLabel.text = "\(indexPath.row + 1)."
cell.interestRateChangedHandler = { [weak self] in
if let interestText = cell.interestRateTextField.text {
if let interest = Double(interestText){
self?.interestRateArray[indexPath.row] = interest
} else {
self?.interestRateArray[indexPath.row] = nil
}
} else {
self?.interestRateArray[indexPath.row] = nil
}
}
return cell
}