How do you assign a string value to a property in another class in Swift?

Question

I've got some swift code that looks like this:

class GeoRssItem
{
    var title = ""
    var description = ""
}

In another class I declare a variable of this as:

var currentGeoRssItem : GeoRssItem?    // The current item that we're processing

I allocate this member variable as:

        self.currentGeoRssItem = GeoRssItem();

then when I try to assign a property on the self.currentGeoRssItem Xcode auto completes to this:

        self.currentGeoRssItem.?.description = "test"

Which then fails with a build error as so:

"Expected member name following '.'"

How do I set this property? I've read the docs but they aren't very helpful.

Markus Persson · Accepted Answer · 2014-06-13 14:16:05Z

1

The question mark is in the wrong place. Should be:

self.currentGeoRssItem?.description = "test"

However you might get: "Cannot assign to the result of this expression". In that case you need to check for nil like this:

if let geoRssItem = self.currentGeoRssItem? {
    geoRssItem.description = "test"
}

answered Jun 13, 2014 at 14:16

Markus Persson

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1 Comment

Matt Gibson Over a year ago

Yup; “...you can use optional chaining to access a property on an optional value, and to check if that property access is successful. You cannot, however, set a property’s value through optional chaining.” — The Swift Programming Language, "Optional Chaining".

Bill · Accepted Answer · 2014-06-13 14:25:02Z

0

If you want to assert that the value is non-nil, you can do:

self.currentGeoRssItem!.description = "test"

If you want the statement to be a no-op if the variable is nil, then

self.currentGeoRssItem?.description = "test"

answered Jun 13, 2014 at 14:25

Bill

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1 Comment

Lee Over a year ago

The ! works, but using the ? results in the error "Cannot assign to the result of this expression"

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