optional tag

3 questions

1 answers
85 views
0

Why is it optional here?

I want to write the code for moving the screen@IBAction funcgoSecond(_sender:Any){ 　　let secondVC = self.storyboard ?.instantiateViewController (withIdentifier: second) 　　present(secondVC!, animated:t...

swift swift3 optional

1 years ago

2 answers
94 views
0

The process of switching an image tapped in the IF statement of SWIFT to another image.

I want to switch to PAUSE image when I tap START image as attached image, but I can't.追Additional The build passes through the xcode, but when I tap the START image, it does not switch to the PAUSE im...

swift xcode swift4 optional

1 years ago

1 answers
114 views
0

Not sure if the type defined in aws-sdk-js is correct

In the S3 client module of AWS, there is a function below, but if you write this way, the error will surely enter the callback, so it should be err?:Error.It makes me think thatupload(params:S3.Types....

typescript optional

1 years ago

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