Swift: Dynamic Object Creation

Question

I am trying to create objects dynamically based on the output of an XML file. My apologies if there are other posts on this subject, I don't even know what this is called. Basically I want to create a stack of objects that could be of any class. In a nutshell, when the "didStartElement" of the NSXMLParser is called, I want to create an object of type "elementName" and stack it to my object stack. The code below is not working, just trying to illustrate what I am trying to accomplish. Normally I would just put "objectStack.append(object) as object" but in this case I don't know what the object type is going to be until the element is scanned by the XML parser. I believe the NSClassFromString is the way to do this, but it's not working.

func parser(parser: NSXMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

    objectStack.append(NSClassFromString(elementName))

}

Any assistance would be greatly appreciated. Even if you can just point me in the right direction.

When you say its not working? Whats the error you are getting? I think you need to actually alloc & init the object, try objectStack.append(NSClassFromString(elementName)()) note the extra (). — sbarow
– sbarow, Commented Jul 22, 2016 at 21:50
Just solved the issue, I was really close. I just need to prepend the project name in front of the element name. Working code to follow. — GED125
– GED125, Commented Jul 22, 2016 at 21:55

GED125 · Accepted Answer · 2016-07-22 21:57:51Z

1

Got it working, the problem was that I needed the fully qualified name of the class, with the project name.

Working code:

var objectStack = [AnyClass]()
func parser(parser: NSXMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

    var className = String(NSString(format: "MyProject.%@", elementName))
    objectStack.append(NSClassFromString(className)!)
}

answered Jul 22, 2016 at 21:57

GED125

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2 Comments

Luke Van In Over a year ago

Does this work for NSObject, AnyObject, Any, struct, and/or type aliases.

GED125 Over a year ago

To be honest I haven't tried. I only used this on NSObject. My code has changed again to init the object. I can post the updated code if you would like.

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