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Why can't I use the try? in swift


try, try! & try? what’s the difference, and when to use each?How to call Objective-C code from Swift#ifdef replacement in the Swift language@selector() in Swift?#pragma mark in Swift?How can I extend typed Arrays in Swift?Swift for loop: for index, element in array?Swift Beta performance: sorting arraysSwift do-try-catch syntaxSwift 2: Call can throw, but it is not marked with 'try' and the error is not handledexception handling with swift






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-4















Use try? to handling the error in the function
But it shows that "No calls to throwing functions occur within 'try' expression"



 if let result:Double = try? finalformular.expression.expressionValue(with: nil, context: nil) as! Double
text = String(result)
else
text = "Error"



enter image description here










share|improve this question

















  • 1





    expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

    – Larme
    Mar 23 at 7:38







  • 1





    Possible duplicate of try, try! & try? what’s the difference, and when to use each?

    – El Tomato
    Mar 23 at 7:41

















-4















Use try? to handling the error in the function
But it shows that "No calls to throwing functions occur within 'try' expression"



 if let result:Double = try? finalformular.expression.expressionValue(with: nil, context: nil) as! Double
text = String(result)
else
text = "Error"



enter image description here










share|improve this question

















  • 1





    expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

    – Larme
    Mar 23 at 7:38







  • 1





    Possible duplicate of try, try! & try? what’s the difference, and when to use each?

    – El Tomato
    Mar 23 at 7:41













-4












-4








-4








Use try? to handling the error in the function
But it shows that "No calls to throwing functions occur within 'try' expression"



 if let result:Double = try? finalformular.expression.expressionValue(with: nil, context: nil) as! Double
text = String(result)
else
text = "Error"



enter image description here










share|improve this question














Use try? to handling the error in the function
But it shows that "No calls to throwing functions occur within 'try' expression"



 if let result:Double = try? finalformular.expression.expressionValue(with: nil, context: nil) as! Double
text = String(result)
else
text = "Error"



enter image description here







swift






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 23 at 7:34









Nick ShernNick Shern

11




11







  • 1





    expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

    – Larme
    Mar 23 at 7:38







  • 1





    Possible duplicate of try, try! & try? what’s the difference, and when to use each?

    – El Tomato
    Mar 23 at 7:41












  • 1





    expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

    – Larme
    Mar 23 at 7:38







  • 1





    Possible duplicate of try, try! & try? what’s the difference, and when to use each?

    – El Tomato
    Mar 23 at 7:41







1




1





expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

– Larme
Mar 23 at 7:38






expressionValue(with:, context:) really throws? What's its declaration? Seems to be developer.apple.com/documentation/foundation/nsexpression/… there is no "throws", so no reason to do a try.

– Larme
Mar 23 at 7:38





1




1





Possible duplicate of try, try! & try? what’s the difference, and when to use each?

– El Tomato
Mar 23 at 7:41





Possible duplicate of try, try! & try? what’s the difference, and when to use each?

– El Tomato
Mar 23 at 7:41












1 Answer
1






active

oldest

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0














As error explains, there isn't any method which would throw. If you're using optional binding, you just need to use as? Double since you don't know if return type is Double and you need to downcast it



if let result = finalformular.expression.expressionValue(with: nil, context: nil) as? Double 
text = String(result)
else
text = "Error"






share|improve this answer

























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    1 Answer
    1






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    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0














    As error explains, there isn't any method which would throw. If you're using optional binding, you just need to use as? Double since you don't know if return type is Double and you need to downcast it



    if let result = finalformular.expression.expressionValue(with: nil, context: nil) as? Double 
    text = String(result)
    else
    text = "Error"






    share|improve this answer





























      0














      As error explains, there isn't any method which would throw. If you're using optional binding, you just need to use as? Double since you don't know if return type is Double and you need to downcast it



      if let result = finalformular.expression.expressionValue(with: nil, context: nil) as? Double 
      text = String(result)
      else
      text = "Error"






      share|improve this answer



























        0












        0








        0







        As error explains, there isn't any method which would throw. If you're using optional binding, you just need to use as? Double since you don't know if return type is Double and you need to downcast it



        if let result = finalformular.expression.expressionValue(with: nil, context: nil) as? Double 
        text = String(result)
        else
        text = "Error"






        share|improve this answer















        As error explains, there isn't any method which would throw. If you're using optional binding, you just need to use as? Double since you don't know if return type is Double and you need to downcast it



        if let result = finalformular.expression.expressionValue(with: nil, context: nil) as? Double 
        text = String(result)
        else
        text = "Error"







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Mar 23 at 8:34

























        answered Mar 23 at 7:53









        Robert DreslerRobert Dresler

        8,3652727




        8,3652727





























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