Advanced Application of nsarray in iOS-filter.

 

C/C ++ developers must like to use the boost library, which has powerful container functions. In iOS development, array is also equivalent to a container and has powerful functions. Nsarray can use nspredicate to filter the array content. nspredicate is a bit like SQL + regular expression. The specific syntax is not mentioned here. I will Google it myself.

 

I don't want to type (I'm super lazy). Use the code to speak:

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1. // Find an array
2. Nsfilemanager * filemanager = [nsfilemanager defaultmanager];
3. Nsstring * defaultpath = [[nsbundle mainbundle] resourcepath];
4. Nserror * error;
6. Nsarray * directorycontents = [filemanager contentsofdirectoryatpath: defaultpath error: & error]
7. // Matches the string and returns the reverse result. Self = indicates each element in the array.
   
8. Nsstring * match = @ "imagexyz-999.png ";
9. Nspredicate * predicate = [nspredicate predicatewithformat: @ "Self = % @", Match];
10. Nsarray * Results = [directorycontents filteredarrayusingpredicate: predicate];
12. // Approximate match string, similar to the syntax in SQL
13. Nsstring * match = @ "imagexyz *. PNG ";
14. Nspredicate * predicate = [nspredicate predicatewithformat: @ "self like % @", Match];
15. Nsarray * Results = [directorycontents filteredarrayusingpredicate: predicate];
16. // Case-insensitive matching
17. Nsstring * match = @ "imagexyz *. PNG ";
18. Nspredicate * predicate = [nspredicate predicatewithformat: @ "self like [cd] % @", Match];
19. Nsarray * Results = [directorycontents filteredarrayusingpredicate: predicate];
20. // Regular Expression matching
21. Nsstring * match = @ "imagexyz-// d {3} //. PNG ";
22. Nspredicate * predicate = [nspredicate predicatewithformat: @ "Self matches % @", Match];
23. Nsarray * Results = [directorycontents filteredarrayusingpredicate: predicate];