> I can't understand this. For me ValuePreservingStringConvertible usually will
> be different than CustomStringConvertible. Can't I want to have some string
> view of my struct to present data(also in UI) *and* value preserving string
> value for the same struct?
> So my .description will show something like "12.345-6.78" and value
> preserving string will contain something like "19083749347923847293487293483"
> to encode the data of the struct. No?
Rather than thinking of LosslessStringConvertible as a protocol for serializing
data into a string, think of it as a protocol for those cases where the
human-readable description is also parseable and can be used to completely
recreate the instance. It's something you would use for things like
command-line arguments, environment variables, interactive command-line
programs, and configuration files that you expect humans to read and write by
hand.
func prompt<T: LosslessStringConvertible>(for field: String, of type:
T.Type) -> T {
while true {
print("What's your \(field)?")
let line = readline()
if !line.isEmpty
let value = T(line) { // how the hell
do you indent this stupid syntax?
return value
}
}
}
let name = prompt(for: "name", of: String)
let age = prompt(for: "age", of: Int)
let answer = age < 13 ? " not" : ""
print("\(name), you are\(answer) too old to have a favorite color.")
In other words, write the `description` first, and then decide if you can write
a good `init(_ description:)` to match it.
--
Brent Royal-Gordon
Architechies
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