SBJson 4: Don't make me wait!

How SBJson 4 can help you get happy users.

Transcript

1. SBJson 4: Don’t make me wait! Stig Brautaset ~ @stigbra
2. Who am I? Started SBJson in 2007. Compulsively tinkered with it since.
3. Fun facts 7 years on • 1012 commits • 4 major releases • 30 contributors • 3247 “stars” • 688 “forks”
4. –Every non-trivial app, ever. “Download a list of records & display them to the user.”
5. What’s more important to your users? • Time until they see the last record? • Or until they see the first?
6. The trouble with pagination • Repeated connection overhead • Records fall in the cracks between pages • Records appear on two consecutive pages
7. Download-then-parse Time to first record Time to last record
8. Chunked delivery Time to first record Time to last record
9. Multi-core chunked delivery Time to first record Time to last record
10. Relative time to first record 0 1.25 2.5 3.75 5 1 record 2 records 3 records 4 records 5 records Chunked delivery Traditional
11. NSJSONSerialisation • Supports NSStream! • But can’t do chunked delivery. • We can do better!
12. SBJson 3 • Chunked delivery since June 2011 :-) • But it was confusing and cumbersome to use… :-/ • …requiring multiple delegates chained together :-(
13. SBJson 4 • Drops category & OO interfaces • Focus on chunked delivery • Introduces a block-based interface • Built specifically for two primary use cases
14. Multi-root JSON [1,2,3] {“foo”:42} [true,false]
15. Multi-root JSON id parser =
 [SBJson4Parser
 multiRootParserWithBlock:block
 errorHandler:eh];
16. Multi-root JSON [parser parse:data("[]{")];
 // calls block(@[]) [parser parse:data("}[]"]; // next part of stream
 // calls block(@{})
 // calls block(@[])
17. Multi-root JSON [parser parse:data("[]{")];
 // calls block(@[]) [parser parse:data("}[]"]; // next part of stream
 // calls block(@{})
 // calls block(@[])
18. Compromise: “garbage after JSON” []**xx block(@[])
 errorHandler(…)
19. –Johnny Appleseed “What if I am using a 3rd-party API that just gives me a long list?”
20. Root array chunks [ [1,2,3], {“foo”:42}, [true,false] ]
21. Unwrap the root array! id parser =
 [SBJson4Parser
 unwrapRootArrayParserWithBlock:block
 errorHandler:eh];
22. Unwrap the root array! [parser parse:data("[[],{")];
 // calls block(@[]) [parser parse:data("},true]")];
 // calls block(@{})
 // calls block(@(YES))
23. Unwrap the root array! [parser parse:data("[[],{")];
 // calls block(@[]) [parser parse:data("},true]")];
 // calls block(@{})
 // calls block(@(YES))
24. Compromise: Corrupted / incomplete JSON [
 {},
 [],
 ***###$#”>P block(@{})
 block(@[])
 errorHandler(…)
25. Unwrapping is for root-level arrays only!
26. SBJson’s Blocks SBJson4ValueBlock block = ^(id obj, BOOL *stop) {
 if (some_condition) {
 *stop = YES;
 } else {
 // do something with obj
 }
 };
27. SBJson4ParserStatus switch ([parser parse:data]) {
 case SBJson4ParserStopped:
 case SBJson4ParserComplete:
 NSLog(“Done!");
 case SBJson4ParserWaitingForData:
 break;
 case SBJson4ParserError:
 NSLog(@"Ouch, I'm hurt!");
 break;
 }
28. Use with custom
 NSURLSessionDataDelegate - (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dt didReceiveData:(NSData *)data { 
 switch ([parser parse: data]) { // handle various returns here… } }
29. Two CocoaPods! To allow both version 3 and 4 in the same application.
30. http://www.flickr.com/photos/dullhunk/202872717/