Why app crashes if year is less than 1948 or more than 2086? - ios

Question

My Xcode app crashes if the user inputs a year below 1948 or for example more than the year 2086 and was wondering if anyone had this issue before and how to resolve?
The user selects their date of birth and the app displays data such as the number of seconds between today's date and their date of birth.
I am new to Xcode (Xcode 8) so still learning. Thanks in advance
#IBAction func clickScreenBtn(_ sender: Any) {
let birthDay = UserDefaults.standard.object(forKey: "birthday") as! Date
var component = NSCalendar.current.dateComponents([.day], from: birthDay, to: Date())
type = type + 1
switch type {
case 0:
unitLabel.text = "Days"
timeLabel.text = ""
timeLabel.text = timeLabel.text?.appendingFormat("%d", component.day!)
break
case 4:
type = 0
unitLabel.text = "Days"
timeLabel.text = ""
timeLabel.text = timeLabel.text?.appendingFormat("%d", component.day!)
break
case 1:
component = NSCalendar.current.dateComponents([.hour], from: birthDay, to: Date())
unitLabel.text = "Hours"
timeLabel.text = ""
timeLabel.text = timeLabel.text?.appendingFormat("%d", component.hour!)
break
case 2:
component = NSCalendar.current.dateComponents([.minute], from: birthDay, to: Date())
unitLabel.text = "Minutes"
timeLabel.text = ""
timeLabel.text = timeLabel.text?.appendingFormat("%d", component.minute!)
break
case 3:
component = NSCalendar.current.dateComponents([.second], from: birthDay, to: Date())
unitLabel.text = "Seconds"
timeLabel.text = ""
timeLabel.text = timeLabel.text?.appendingFormat("%d", component.second!)
break
default:
break
}
}
Error:
0x108142301 <+9425>: callq 0x1082a95c4 ; symbol stub for: Foundation.Calendar.dateComponents (Swift.Set<Foundation.Calendar.Component>, from : Foundation.Date, to : Foundation.Date) -> Foundation.DateComponents
0x108142306 <+9430>: movq -0x710(%rbp), %rdi
0x10814230d <+9437>: movq %rax, -0x730(%rbp)
0x108142314 <+9444>: callq 0x10813d8a0 ; swift_rt_swift_release
0x108142319 <+9449>: movq -0x730(%rbp), %rax
0x108142320 <+9456>: movq %rax, -0x8(%rbp)
0x108142324 <+9460>: movq -0x218(%rbp), %rdi
0x10814232b <+9467>: callq 0x10813d8a0 ; swift_rt_swift_release
0x108142330 <+9472>: movq 0x1e3081(%rip), %rax ; (void *)0x000000010e87f068: swift_isaMask
0x108142337 <+9479>: movq -0x168(%rbp), %rdx
0x10814233e <+9486>: movq (%rdx), %rdi
0x108142341 <+9489>: andq (%rax), %rdi
0x108142344 <+9492>: movq %rdi, -0x738(%rbp)
0x10814234b <+9499>: movq %rdx, %rdi
0x10814234e <+9502>: movq -0x738(%rbp), %rax
0x108142355 <+9509>: callq *0x80(%rax)
0x10814235b <+9515>: movq %rax, -0x70(%rbp)
0x10814235f <+9519>: movq -0x230(%rbp), %rax
0x108142366 <+9526>: movsd -0x1d8(%rbp), %xmm0 ; xmm0 = mem[0],zero
0x10814236e <+9534>: movd %xmm0, %rax
0x108142373 <+9539>: cmpq $0x0, -0x70(%rbp)
0x108142378 <+9544>: jne 0x108142409 ; <+9689> at MainViewController.swift
0x10814237e <+9550>: movq -0x230(%rbp), %rax
0x108142385 <+9557>: movsd -0x1d8(%rbp), %xmm0 ; xmm0 = mem[0],zero
0x10814238d <+9565>: movd %xmm0, %rax
0x108142392 <+9570>: movq -0x230(%rbp), %rax
0x108142399 <+9577>: movsd -0x1d8(%rbp), %xmm0 ; xmm0 = mem[0],zero
0x1081423a1 <+9585>: movd %xmm0, %rax
0x1081423a6 <+9590>: movq -0x230(%rbp), %rax
0x1081423ad <+9597>: movsd -0x1d8(%rbp), %xmm0 ; xmm0 = mem[0],zero
0x1081423b5 <+9605>: movd %xmm0, %rax
0x1081423ba <+9610>: leaq 0x1b13f9(%rip), %rdi ; "fatal error"
0x1081423c1 <+9617>: movl $0xb, %eax
0x1081423c6 <+9622>: movl %eax, %esi
0x1081423c8 <+9624>: movl $0x2, %eax
0x1081423cd <+9629>: leaq 0x1b13ac(%rip), %rcx ; "unexpectedly found nil while unwrapping an Optional value"
0x1081423d4 <+9636>: movl $0x39, %edx
0x1081423d9 <+9641>: movl %edx, %r8d
0x1081423dc <+9644>: xorl %edx, %edx
0x1081423de <+9646>: movl %edx, -0x73c(%rbp)
0x1081423e4 <+9652>: movl %eax, %edx
0x1081423e6 <+9654>: movl %eax, %r9d
0x1081423e9 <+9657>: movl $0x0, (%rsp)
0x1081423f0 <+9664>: callq 0x1082a95f4 ; symbol stub for: function signature specialization <preserving fragile attribute, Arg[2] = Dead, Arg[3] = Dead> of Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, file : Swift.StaticString, line : Swift.UInt, flags : Swift.UInt32) -> Swift.Never
0x1081423f5 <+9669>: movq -0x230(%rbp), %rcx
0x1081423fc <+9676>: movsd -0x1d8(%rbp), %xmm0 ; xmm0 = mem[0],zero
0x108142404 <+9684>: movd %xmm0, %rcx
0x108142409 <+9689>: leaq -0x70(%rbp), %rax
0x10814240d <+9693>: movq -0x70(%rbp), %rcx
0x108142411 <+9697>: movq %rcx, %rdi
0x108142414 <+9700>: movq %rax, -0x748(%rbp)
0x10814241b <+9707>: movq %rcx, -0x750(%rbp)
0x108142422 <+9714>: callq 0x1082a9858 ; symbol stub for: objc_retain
0x108142427 <+9719>: leaq 0x1b1398(%rip), %rdi ; "Seconds"

Answer 1

If you get rid of all the !s and replace them with some actual error checking, you should be able to find out where the error is occurring rather quickly. For example, this version will log whatever is going wrong to the console:
#IBAction func clickScreenBtn(_ sender: Any) {
guard let birthDay = UserDefaults.standard.object(forKey: "birthday") as? Date else {
print("Couldn't get birthday")
return
}
let currentDate = Date()
guard let day = Calendar.current.dateComponents([.day], from: birthDay, to: currentDate).day else {
print("Couldn't get day")
return
}
type = type + 1
switch type {
case 0:
unitLabel.text = "Days"
timeLabel.text = "\(day)"
case 4:
type = 0
unitLabel.text = "Days"
timeLabel.text = "\(day)"
case 1:
guard let hour = Calendar.current.dateComponents([.hour], from: birthDay, to: currentDate).hour else {
print("Couldn't get hour")
return
}
unitLabel.text = "Hours"
timeLabel.text = "\(hour)"
case 2:
guard let minute = Calendar.current.dateComponents([.minute], from: birthDay, to: currentDate).minute else {
print("Couldn't get minute")
return
}
unitLabel.text = "Minutes"
timeLabel.text = "\(minute)"
case 3:
guard let second = Calendar.current.dateComponents([.second], from: birthDay, to: currentDate).second else {
print("Couldn't get second")
return
}
unitLabel.text = "Seconds"
timeLabel.text = "\(second)"
default:
break
}
}
Once you know where the issue is actually occurring, it should be much easier to fix it.