1. In order to ensure the absolute security of its own data, the Apple mobile phone has designed a sandbox file . Each application is equipped with its own sandbox file . Every time it is run , the name of the folder will become an irregular character. string
The first parameter : which folder to go to currently , go to the documents file with NSDocumentDirectory: line 64 , you can also go to the caches folder : corresponding to line 68
The second parameter : the type of folder accessed , specify the user folder when accessing
The third parameter
Absolute path (YES): It is used by the system . The system can find the folder according to the current path . We use absolute paths when manipulating files.
Relative path (NO hardly needed ): The relative path will only show the folder you want to go to , and the other parts are ~, telling the programmer which file to go
2. There are three folders in the sandbox
(1) is Documents files : mainly want to store some of the information used to store the user , such as the collection of information or something set up their own , so we do the collection function is to write something to the file folder
(2) Library folder is easy to program developers to use , mainly to operate it in two folders , caches and Preferences
caches: Used to save cache files , SDWebImage will add pictures to the cache files , so the clear cache function is to delete this folder
Preferences generally save the information set by the programmer , for example, NSUserDefaults will save the data in this folder
(3) tmp file : generally store temporary content
Before there is a sandbox .app file , the new version has been removed