Sorting array gives me error

Question

I have an array of structs. In the struct I have two NSDate objects: prop1 and prop2. I'm trying to sort prop1 from newest to oldest date/time. And I want prop2 to also get ordered based on prop1. (I will also want to do vice versa.)

struct Item {
    let prop1 : NSDate
    let prop2 : NSDate
}

var myItem = [Item]()

myItem.insert(Item(prop1: myDateSecond, prop2: anotherDateSecond), atIndex: 0)
myItem.insert(Item(prop1: myDateThird, prop2: anotherDateThird), atIndex: 0)
myItem.insert(Item(prop1: myDateFirst, prop2: anotherDateFirst), atIndex: 0)

myItem.sort { $0.prop1 < $1.prop1 }

At the last line of code, I get the following error:

Cannot invoke 'sort' with an argument list of type '((_, _) -> _)'

What am I doing wrong, and how can I fix it?

What's array in array.sort?

Lyndsey Scott
– Lyndsey Scott

2015-08-31 02:07:15 +00:00
Commented Aug 31, 2015 at 2:07 — Lyndsey Scott
– Lyndsey Scott, Commented Aug 31, 2015 at 2:07
My bad. I just changed it to myItem.sort

Jessica
– Jessica

2015-08-31 02:10:12 +00:00
Commented Aug 31, 2015 at 2:10 — Jessica
– Jessica, Commented Aug 31, 2015 at 2:10

Leo Dabus · Accepted Answer · 2015-08-31 02:20:11Z

1

When comparing two dates you have to use NSDate method compare:

struct Item {
    let prop1 : NSDate
    let prop2 : NSDate
}

var myItem = [Item]()

myItem.insert(Item(prop1: myDateSecond, prop2: anotherDateSecond), atIndex: 0)
myItem.insert(Item(prop1: myDateThird, prop2: anotherDateThird), atIndex: 0)
myItem.insert(Item(prop1: myDateFirst, prop2: anotherDateFirst), atIndex: 0)

myItem.sort{$0.prop1.compare($1.prop1) == NSComparisonResult.OrderedAscending}

edited Aug 31, 2015 at 2:20

answered Aug 31, 2015 at 2:11

Leo Dabus

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3 Comments

Jessica Over a year ago

Thanks for the answer! Can you please include the longer version of sort? This one is a bit confusing and hard to read. Thanks!

Leo Dabus Over a year ago

Thats basic Swift syntax. I've posted the documentation's link to the compare method.

Jessica Over a year ago

I'm talking about $0.prop1.compare($1.prop2)

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