Swift beginners-advanced syntax and swift beginners

Swift beginners-advanced syntax and swift beginners

Default Binding (Optional Binding is automatically set to null)

Add ?, Nil can be bound by default.

Var window: UIWindow?

That is to say, if the value of window is not assigned, the value of window is nil.

This is different from the principle of automatic nil setup in the ARC mode in Objective-C. NilType exists in Swift, and its inverse operation is Unwrapping Optionals)

Value (Unwrapping Optionals)

Available! Remove the non-null values in the window variable (which has been bound by default). Be sure to set the value of the non-null type. Otherwise, a running error is reported.

Default chain

Use Unowned References to solve circular References

Syntax problems in taylor swift lyrics

There is a commonly used method for omitting the title of a newspaper. The active method uses ing and the passive method uses the past word segmentation.
For example, stuck in traffic is a traffic jam.
This is similar, but it is more about rhyming. It is very common to omit the lyrics. Chinese lyrics are not very syntactic.
Complete should be I have been ....
Or the Passive Meaning of "I am stuck here but you cannot see it"
However, regular articles cannot be used.
This is my idea for reference.
Haha ..........

Syntax in the lyrics of taylor swift's red album

Generally, the lyrics do not focus on syntaxes, or even some syntaxes are incorrect. Therefore, it is not good to listen to English songs and learn grammar.