Xcode 9.3-NSPredicate Bool崩溃

Question

After the Xcode 9.3 update, I've noticed that if you want to have Predicate like this:

let predicate = NSPredicate(format: "preferred = %@", true as CVarArg)

You have a crash. But in Xcode 9.2 this wasn't a problem. Any idea?

Answer 1

// Solution 3 [ Apple Documentation ]

let predicate = NSPredicate(format: "preferred == TRUE")

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The exception occurs because true is not an object ( %@ ). You need the %d placeholder

let predicate = NSPredicate(format: "preferred = %d", true)

Answer 2

After a bit of investigation, I've discovered how to fix this. In short:

// Solution 1 [ NSNumber ]
let bool = NSNumber(booleanLiteral: true)
let predicate = NSPredicate(format: "preferred = %@", bool as CVarArg)

// Solution 2 [ Bool ] (static example)
let predicate = NSPredicate(format: "preferred == YES")

As also explained here , it's simply better to deal with Obj-C type instead of Swift type when we have to deal with this kind of methods.

Answer 3

我认为您也可以使用此：

NSPredicate(format: "preferred = true")