I define a struct as follows:
struct MyModel : Decodable {
var id : Int
var amount: Int
let myNewTableId : Int
let userId : Int
let myNewTable : MyNewTable
}
I then use this struct to convert JSON data into an object using JSONDecoder().decode.
The problem is that the myNewTable part of myNewTableId and myNewTable are based on an alias given to the SQL table they originate from. So if the alias is abc the fields should be abcId and abc and if its def it should be defId and def. I've saved this alias into a variable:
let MY_NEW_TABLE_ALIAS = "myNewT"
Is there a way to construct the variable names in the struct dynamically using MY_NEW_TABLE_ALIAS. Ideally, when the alias changes on the SQL side, I just want to update one variable, instead of having to update every single struct which uses that table.
The simple way is to convert the json first to a string and replace occurrences with the needed key / use CodingKeys and make the struct as it is , btw you can't have dynamic variable names
Related
So I am getting a warning (and I can't dismiss it because it won't run the JSON if I do)
The warning is for the following
struct Station: Codable, Identifiable {
let id = UUID() // WARNING: Immutable property will not be decoded because it is declared with an initial value which cannot be overwritten
var name : String
var imageurl : String
var listenlive : String
}
The problem is the following
I can't make it UUID as I get the following error
Type 'Station' does not conform to protocol 'Decodable'
// STATION
struct Sdata: Codable {
var data: [Station]
}
struct Station: Codable, Identifiable {
let id = UUID
var name : String
var imageurl : String
var listenlive : String
}
Also technically the let id is wrong because the JSON has it as _id
"_id":"5f52ed668b964609655b48d1"
So How do I make the warning go away while conforming to the correct value type?
In this case, it's not a matter of "getting rid of the warning". What you are doing seems fundamentally wrong.
The way you declared struct Station, every time a new struct is created, its "id" field is set to a new UUID, that is every struct Station has a different id field, that cannot be changed afterwards.
So if we ignore Codeable for the moment, how would you write such a struct to a file and read it back later, getting the same id? Answer: You can't read it back. At some point you create a struct Station with a new, different UUID, and there is no way to store the one that you wrote to a file. So you have a problem here.
So the problem is quite obvious: If you have a "let" property with a non-constant value, Codeable would have to write it, but Decodable cannot read it, so you have a problem. Make "id" a var, possibly with a constructor that sets it to a new UUID, but it must be changeable.
You need to change it to id:String and use enum CodingKeys for the custom name _id
struct Station: Codable , Identifiable {
var id,name,imageurl,listenlive:String
private enum CodingKeys : String, CodingKey {
case id = "_id", name , imageurl , listenlive
}
}
I currently have a random number generator in my url that is used to assign new numbers to the page parameter of the url. When I fetch a new image and print the url, it uses the same url. I do not know how to approach removing the existing random number in the url.
Here is my declaration:
public static var random = Int.random(in: 0..<450)
static let ImageURL = "https://api.unsplash.com/search/photos/?client_id=\(UnsplashClient.apiKey)&page=\(random))"
Do not use static for your array. Static variables only generated once. So it does not generate random numbers for you.
read this: When to use static constant and variable in Swift?
According to me, You have to create a array of numbers that contains integers from 0 to 450 like this var array = Array(0...450) and and then can select random number from that array using array.randomElement()!. And after selecting, remove that number from that array.
Since you're using a static property and it's value is not gonna change each time you call it, unless you update it manually. You can fix this issue by using static computed property whose value is computed everytime it's used.
public static var random: Int { .random(in: 0..<450) }
public static var ImageURL: String { "https://api.unsplash.com/search/photos/?client_id=\(UnsplashClient.apiKey)&page=\(random))" }
Or you can combine them as #leo has mentioned in the comments, if you don't have any other purpose for random, like this:
public static var imageURL: String { "https://api.unsplash.com/search/photos/?client_id=\(UnsplashClient.apiKey)&page=\(Int.random(in: 0..<450)))" }
I am new to Swift and I have data I'd like to call from an API through JSON. For some strange reason some of the names are written with whitespaces making it difficult for me to declare variables that'll show the integer type value they hold. Here is a screenshot . I am trying to parse the Int value attached to the type "Anti-social behaviour" but don't seem to know how to declare it appropriately.
You can define your own CodingKeys inside the file. Note that the name should be CodingKeys.
struct Types: Codable {
let buglary: Int
let shoplifting: Int
let drugs: Int
let robbery: Int
let antiSocialBehavior: Int
// Other properties
enum CodingKeys: String, CodingKey {
case buglary = "Buglary"
case shoplifting = "Shoplifting"
case drugs = "Drugs"
case robbery = "Robbery"
case antiSocialBehavior = "Anti-social behavior"
// other coding keys
}
}
Also, note that properties in Swift are always camelcased and not capitalized. So, I also changed the name of your properties. Check the enum inside the struct which actually defines the mapping between property name and their encoding / decoding keys.
I have a service that returns this JSON structure "actual-price": {,
I want to know if it is possible to create a variable like JS with Codable on swift.
PS: I can't change the JSON since the service is not mine
You will need to use a CodingKeys enumeration to map the jSON properties to valid Swift properties. Note that once you introduce a CodingKeys enumeration it must contain all of the properties you wish to map, not just the properties where you want to change the name.
Something like
struct MyStruct: Codable {
var actualPrice: Double
var quantity: Int
enum CodingKeys: String, CodingKey {
case actualPrice = "actual-price"
case quantity = "quantity"
}
}
I had some older Swift code that used to compile and work where I was using the .append to build out a data structure dynamically. After upgrading to a few compiler versions newer I am getting the dreaded "Extra Argument ' ' in call" error. I reduced the code down to this:
struct EHSearch {
let EHcategory : String = ""
let EHname : String = ""
}
var myEHSearch = [EHSearch]()
// Call to dynamically append the results
// Extra argument: 'EHcategory' in call
myEHSearch.append(EHSearch(EHcategory: "Food", EHname: "Joes Crab Shack"))
I can't see anything so far in searching on what has changed to cause this one so seeking guidance here.
Because you have let in your struct.
Define your structure like this:
struct EHSearch {
var EHcategory : String = ""
var EHname : String = ""
}
If you have constants in your struct, you can not provide them initial value while creating new structure instances. The automatically-generated member-wise initializer doesn't accept let members as parameters of the initializer of struct.
It depends on your intentions with the struct's properties. Do you want them to be mutable or not?
If yes, then #sasquatch's answer will do.
If not, then you need to ensure a value is assigned to them only once. As you already do that in the struct declaration (the default values), you can't assign new values to them. But being a struct, they don't need to have default values - moreover, struct automatically receive a memberwise initializer. https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html
So here is the variant for immutable properties:
struct EHSearch {
let EHcategory : String
let EHname : String
}
var myEHSearch = [EHSearch]()
// Call to dynamically append the results
// Extra argument: 'EHcategory' in call
myEHSearch.append(EHSearch(EHcategory: "Food", EHname: "Joes Crab Shack"))
The "Extra Argument" error you're seeing is because the compiler already has values for the properties so it doesn't expect any new ones. Here is the "middle" way - one property has a default value whilst the other doesn't - which should make it clearer:
struct EHSearch {
let EHcategory : String = ""
let EHname : String
}
var myEHSearch = [EHSearch]()
// Call to dynamically append the results
// Extra argument: 'EHcategory' in call
myEHSearch.append(EHSearch(EHname: "Joes Crab Shack"))