Converting objective-c codes to swift 4 - ios

Question

it's been 1.5 years i've been writing in obj-c, its a good language.. so i saw a medium article today about swift, really looking onto it, right now i am trying to convert all my obj-c codes to swift, fortunately everything is done expect for this part..
NSString *path = [[NSBundle mainBundle] pathForResource:#"list" ofType:#"plist"];
NSArray *plistData = [NSArray arrayWithContentsOfFile:path];
NSPredicate *filter = [NSPredicate predicateWithFormat:#"english ==[c] %#", self.userQuery.text]; // something like "Abbey"
NSArray *filtered = [plistData filteredArrayUsingPredicate:filter];
NSLog(#"found matches: %# : %#", filtered,[filtered valueForKey:#"kurdi"]);
if (filtered.count>0) {
NSDictionary *dic = filtered[0];
self.theMeaningLabel.text = dic[#"kurdi"];
} else {
self.theMeaningLabel.text = #"Yay!‌";
}
i am not being able to properly convert this into the new swift 4, it gives random errors
EDIT
after a few searches, i could just write two lines of code
here's my swift code
var path: String? = Bundle.main.path(forResource: "list", ofType: "plist")
var plistData = [Any](contentsOfFile: path!)
var filter = NSPredicate(format: "english ==[c] %#", searchText)
// something like "Abbey"
var filtered = plistData?.filter { filter.evaluate(with: $0) }
print("found matches: \(filtered) : \(filtered?.value(forKey: "kurdi"))")
if filtered?.count > 0 {
var dic = filtered[0]
// theMeaningLabel.text = dic["kurdi"]
}
else {
//theMeaningLabel.text = "Yay!‌"
}
but getting the
Argument labels '(contentsOfFile:)' do not match any available overloads
Final edit
var path = Bundle.main.path(forResource:"list", ofType: "plist")
var plistData = NSArray(contentsOfFile: path!)
let filter = NSPredicate(format: "english ==[c] %#", searchText)
var filtered = plistData?.filtered(using: filter)
// [error 9:10] no viable alternative at input 'NSLog(#"found matches: %# : %#"'
if filtered?.count > 0 {
var dic = filtered![0]
// theMeaningLabel.text = dic["kurdi"]
}
else {
// theMeaningLabel.text = "Yay!‌"
}
the code above is fine, but one error comes
if filtered?.count > 0 { // here
var dic = filtered![0]
// theMeaningLabel.text = dic["kurdi"]
}
else {
// theMeaningLabel.text = "Yay!‌"
}
getting
Binary operator '>' cannot be applied to operands of type 'Int?' and 'Int'

Answer 1

A literal translation from Objective-C to Swift is not recommended because in many cases it does not take advantage of the improved semantics of Swift.
As Apple removed all path manipulating API from String and added more URL related API to other classes use always URL if possible
let url = Bundle.main.url(forResource: "list", withExtension: "plist")!
The forced unwrapped url is safe since the file is required to be in the bundle. A crash will reveal a design error and must not happen at runtime.
Unlike the Foundation collection types the Swift collection types don't support the implicit property list conversion so the Swift way is to use Data and PropertyListSerialization
let data = try! Data(contentsOf: url)
let dataArray = try! PropertyListSerialization.propertyList(from: data, format: nil) as! [Any]
The forced try! is as safe as forced unwrapping the url for the same reasons.
[Any] is the most unspecified Swift Array. If the array is supposed to be an array of dictionaries write [[String:Any]] or even [[String: String]] if all values are String. If it's supposed to be an array of Strings write [String]. Swift encourages the developer to be as type specific as possible.
An NSPredicate can be replaced with the filter function in Swift. For example an array of strings can be filtered case insensitively with
let filtered = dataArray.filter { $0.compare(searchText, options:.caseInsensitive) == .orderedSame }
If the array contains dictionaries you need to specify the keys (same as NSPredicate)
let filtered = dataArray.filter { ($0["foo"] as! String).compare(searchText, options:.caseInsensitive) == .orderedSame }
Finally the ObjC expression
if (filtered.count > 0) { ...
can be written much more descriptive in Swift
if filtered.isEmpty == false { ...
or
if !filtered.isEmpty { ...
If you are looking for only one item you can even write
if let foundObject = dataArray.first(where: { $0.compare(searchText, options:.caseInsensitive) == .orderedSame }) { ...