ownerGroupName property Null safety

1. Flutter
2. archive_io
3. TarFile
4. ownerGroupName property

TarFile class

1. Constructors
2. TarFile
3. read
4. Properties
5. checksum
6. content
7. contentBytes
8. deviceMajorNumber
9. deviceMinorNumber
10. filename
11. filenamePrefix
12. fileSize
13. groupId
14. hashCode
15. isFile
16. isSymLink
17. lastModTime
18. mode
19. nameOfLinkedFile
20. ownerGroupName
21. ownerId
22. ownerUserName
23. rawContent
24. runtimeType
25. size
26. typeFlag
27. ustarIndicator
28. ustarVersion
29. Methods
30. noSuchMethod
31. toString
32. write
33. Operators
34. operator ==
35. Constants
36. TYPE_BLOCK_SPEC
37. TYPE_CHAR_SPEC
38. TYPE_CONT_FILE
39. TYPE_DIRECTORY
40. TYPE_EX_HEADER
41. TYPE_EX_HEADER2
42. TYPE_FIFO
43. TYPE_G_EX_HEADER
44. TYPE_G_EX_HEADER2
45. TYPE_HARD_LINK
46. TYPE_NORMAL_FILE
47. TYPE_SYMBOLIC_LINK