What is meaning of "throws" keyword here:
This code take so long to be executed and i think "throws" keyword in the image above related:
let url = URL(string:"\(APIs.postsImages)\(postImg)")
let imgData = try? Data.init(contentsOf: url)
self.postImage.image = UIImage.init(data: imgData)
init() throws can return more information about the failure and let the caller decide if they care about it or not. Read a useful post about it here.
To indicate that a function, method, or initializer can throw an error, you need to write the
throwskeyword in the function’s declaration after its parameters. A function marked withthrowsis called a throwing function. If the function specifies a return type, you write the throws keyword before the return arrow.
func thisFunctionCanThrowErrors() throws -> String
or in real code it might look like this:
enum PossibleErrors: Error {
case wrongUsername
case wrongPassword
}
func loggingIn(name: String, pass: String) throws -> String {
if name.isEmpty {
throw PossibleErrors.wrongUsername
}
if pass.isEmpty {
throw PossibleErrors.wrongPassword
}
return "Fine"
}
The throwing functions like this must be called using one of the following try operators:
Using init() throws you can break the execution of a class initialiser without the need of populating all stored properties:
class TestClass {
let textFile: String
init() throws {
do {
textFile = try String(contentsOfFile: "/Users/swift/text.txt",
encoding: NSUTF8StringEncoding)
catch let error as NSError {
throw error
}
}
}
And in a structure you can even avoid the do/catch block:
struct TestStruct {
var textFile: String
init() throws {
textFile = try String(contentsOfFile: "/Users/swift/text.txt",
encoding: NSUTF8StringEncoding)
}
}
The throws keyword indicates that a function may throw an error. I.e., it is a throwing function. See the documentation for additional details.