swift强制将objective-c int指定为Int32然后崩溃

Question

I have an objective c property that has been declared as

@property int xmBufferSize;

If I do sharedExample.xmBufferSize = 1024 it just works fine but when I am trying to set an integer value for that property from another variable

var getThat:Int = dict["bufferSize"]!.integerValue
sharedExample.xmBufferSize = getThat

It can't do above

Cannot assign a value of type 'Int' to a value of type 'Int32'

If I force this to

sharedExample.xmBufferSize =dict["bufferSize"] as! Int32

It is crashing with Error

Could not cast value of type '__NSCFNumber' to 'Swift.Int32 '

EDIT::::
Dict init, there are other objects in dict besides integers

var bufferSize:Int = 1024
var dict = Dictionary<String, AnyObject>() = ["bufferSize":bufferSize]

Answer 1

The value in dict is an NSNumber , which cannot be cast or directly converted to Int32 . You can first obtain the NSNumber and then call intValue on it:

if let bufferSize = dict["bufferSize"] as? NSNumber {
    sharedExample.xmlBufferSize = bufferSize.intValue
}

The if let … as? allows you to verify that the value is indeed an NSNumber , since (as you said) there can be other types of objects in dict . The then-branch will only execute if dict["bufferSize"] exists and is an NSNumber .

(Note: You can also try integerValue if intValue gives the wrong type, or convert the resulting integer – CInt(bufferSize.integerValue) – as needed. Swift doesn't do implicit conversions between different integer types, so you need to match exactly.)

Answer 2

您需要将NSNumber转换为Int32。

sharedExample.xmBufferSize = dict["bufferSize"]!.intValue

Answer 3

Use type conversion, not as:

sharedExample.xmBufferSize = Int32(dict["bufferSize"] as! Int)

That should work.