unexpectedly found nil unexpectedly - struct init? not working - swift

Question

I am working on a demo app to return a list of restaurant with the google places API.
I have a Restaurant class - 1 property is a custom type RestaurantDetails. This is where the challenge is:
Restaurant.swift
class Restaurant {
var id:String
var placeId:String
var name:String
var location: Location //Location + address + coordinate + distance
var phone:String?
let details : RestaurantDetails
init(id:String, placeId:String, name:String, location: Location, details: RestaurantDetails) {
self.id = id
self.placeId = placeId
self.name = name
self.location = location
self.details = details
}
convenience init(dict:[String:Any]) {
let id = dict["id"] as! String
let placeId = dict["place_id"] as! String
let name = dict["name"] as! String
let address = dict["formatted_address"] as? String
let location = Location(address: address!, json: dict["geometry"] as! [String : Any])
if let price = dict["price_level"] as? Double {
print("price => \(Price(valueDouble: price))")
}
if let rating = dict["rating"] as? Double {
print("rating => \(Rating(valueDouble: rating))")
}
self.init(id: id, placeId: placeId, name: name, location: location!, details: RestaurantDetails(json: dict)!)
}
}
the initialization of the details property fails each time
even using the breakpoint does not help to debug the error because the custom init? does not seem to fire. I do not see any syntax error though
I am usually using guard let control flow to parse the JSON format if the value exists. unsuccessful.
the breakpoint does not kick in on the RestaurantDetails.swift file
RestaurantDetails.swift
enum Price {
case cheap, expensive, `default`
init(valueDouble: Double) {
switch valueDouble {
case 0..<2: self = .cheap
case 2..<4 : self = .expensive
default: self = .default
}
}
var dollarSymbol : String {
switch self {
case .cheap: return "$"
case .expensive: return "$$"
default: return ""
}
}
}
enum Rating {
case low, fair, good, excellent, `default`
init(valueDouble: Double) {
switch valueDouble {
case 0..<2: self = .low
case 3..<4: self = .fair
case 4..<5: self = .good
case 6 : self = .excellent
default: self = .default
}
}
var starSymbol : String {
switch self {
case .low: return "⭐"
case .fair: return "⭐⭐"
case .good: return "⭐⭐⭐"
case .excellent: return "⭐⭐⭐⭐"
default: return ""
}
}
}
struct RestaurantDetails {
let price:Price
let rating:Rating // Rating (enum) (filter)
let openNow: Bool //(filter)
let types : [String]?
let photos : [NSDictionary]?
}
extension RestaurantDetails {
init?(json: [String: Any]) {
guard let price = json["price_level"] as? Double,
let rating = json["rating"] as? Double,
let openingHours = json["opening_hours"] as? NSDictionary,
let types = json["types"] as? [String],
let photos = json["photos"] as? [NSDictionary] else {
return nil
}
print("json details : \(json)")
self.price = Price(valueDouble: price)
self.rating = Rating(valueDouble: rating)
self.openNow = openingHours["open_now"] as! Bool != nil ?? false
self.types = types
self.photos = photos
}
}
I also have a Location.swift file that works perfectly
struct Location {
var address :String
var coordinate:(lat:Double, lng:Double)
}
extension Location {
init?(address: String, json:[String:Any]) {
guard let latitude = json["location"] as? NSDictionary, let longitude = json["location"] as? NSDictionary else { return nil }
self.init(address: address, coordinate: (lat: latitude["lat"] as! Double, lng: longitude["lng"] as! Double))
}
}

Answer 1

As vadian described in his comment, the issue causing the crash is that location has a failable initializer, you are forcibly unwrapping it, and since initialization is in fact failing, you have now force-unwrapped a nil value.
The broader questions are: what do you, the developer, want to happen when some or all location data is not available, and what is the best way to go about doing that?
Options for handling incomplete or missing location data
Based on your description of the problem (“a demo app to return a list of restaurant with the google places api”), it is not clear whether or not restaurants without useable location data should enter your model. It is also not clear whether or not there is some location data you could do without. So I see three options:
Discard all restaurants with incomplete location data
Discard some restaurants with incomplete location data while keeping others
Keep all restaurants regardless of location data
To implement these options, you may want to use some common tools for dealing with optionals:
Nil-coalescing operator
a = b ?? c
Set a equal to b, unless b is nil, in which case set a equal to c.
Optional binding in guard and if
guard let a = b else { return }
Set a equal to b unless b is nil, in which case return from the current context. You can do work in the else branch prior to returning.
if let a = b { /* Do work using a */ } else { /* Do other work */ }
If b is not nil, enter the if branch and set a equal to b; if b is nil, enter the else branch.
How to do it
Discard all restaurants with incomplete location data
In this case, you could make a failable initializer for Restaurant, guarded by location being non-nil:
/// Initialization fails if `location` is `nil`
convenience init?(id:String, placeId:String, name:String, location: Location?, details: RestaurantDetails) {
guard let location = location else { return nil }
self.init(id: id, placeId: placeId, name: name, location: location, details: details)
}
Discard some restaurants with incomplete location data while keeping others
You may be able to recover from some kinds of missing location data. For example, it may be the case that you really just need the street address string and the latitude and longitude are inessential. You could rewrite your Location struct to reflect that:
struct Location {
var address: String
var coordinate: (lat: Double, lng: Double)?
}
extension Location {
init?(address: String, json:[String:Any]) {
let coordinate: (Double, Double)?
if let latitude = json["location"] as? NSDictionary, let longitude = json["location"] as? NSDictionary {
coordinate = (latitude, longitude)
} else {
coordinate = nil
}
self.init(address: address, coordinate: coordinate)
}
}
Alternative, lat/long might be the important part, but it might sometimes be possible to recover them from the street address using another API:
struct Location {
var address: String
var coordinate: (lat: Double, lng: Double)
}
extension Location {
init?(address: String, json:[String:Any]) {
let coordinate: (Double, Double)?
if let latitude = json["location"] as? NSDictionary, let longitude = json["location"] as? NSDictionary {
coordinate = (latitude, longitude)
} else {
/* An API call that takes an address string and tries to return lat/long but might return nil */
coordinate = returnedCoordinateFromAPI
}
guard let coordinate = coordinate else { return nil }
self.init(address: address, coordinate: coordinate)
}
}
Keep all restaurants regardless of location data
This is the easiest case. If location is not essential, make it optional:
class Restaurant {
var id: String
var placeId: String
var name: String
var location: Location? //Location + address + coordinate + distance
var phone: String?
let details: RestaurantDetails
init(id:String, placeId:String, name:String, location: Location?, details: RestaurantDetails) {
self.id = id
self.placeId = placeId
self.name = name
self.location = location
self.details = details
}
convenience init?(dict:[String:Any]) {
guard let id = dict["id"] as? String,
let placeId = dict["place_id"] as? String,
let name = dict["name"] as? String else { return nil }
// Use the address from the dictionary unless it is nil, in which case substitute an empty string
let address = dict["formatted_address"] as? String ?? ""
let location = Location(address: address, json: dict["geometry"] as? [String : Any])
if let price = dict["price_level"] as? Double {
print("price => \(Price(valueDouble: price))")
}
if let rating = dict["rating"] as? Double {
print("rating => \(Rating(valueDouble: rating))")
}
guard let details = RestaurantDetails(json: dict) else { return nil }
self.init(id: id, placeId: placeId, name: name, location: location, details: details)
}
}