Summary of swift optional values

1、 Enumeration structure ;

2、 Pack 、 Unpacking concept ; Association value .

3、 Optional value declaration ;

4、 Unpack ;

5、 Optional values are generated as parameters of the chain .

6、 Optional value call chain .

Finally, make a conclusion

1. When accessing properties or methods of optional objects , It can be used ？ Number
2. When accessing properties of optional objects , from ？ It's all optional , The returned value must be an optional value .
3. When accessing methods of optional objects . Judge whether it is nil To confirm whether the method is called successfully .

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