How to parse NSJsonDictionary objects in json file using SBJson4StreamParser

Question

I'm new to iOS, I was able to write the NSDictionary objects into file like below example

{
"msg":"Hello",
"from":"X",
"date":"12/1/2014"
}
{
"msg":"new to IOS",
"from":"home",
"date":"23/2/2014"
}

I know it is an array of objects I need to be using NSArray, but I have prevented since my one NSDictionary object consumes lot of memory, I wanted to serialise and deserialize one object at a time. I came across SBJson4StreamParser internally does such functionality, but I was facing issues with implementation, I also tried with native NSJsonSeriailzation but options were limited for such type of parsing, can anyone help with this.

Answer 1

SBJson can help here, by reading the file chunkwise with an NSInputStream and feeding it into the parser like this:

id parser = [SBJson4Parser multiRootParserWithBlock:block
                                       errorHandler:eh];

id is = [NSInputStream inputStreamWithFileAtPath:filePath];
[is open];

// Buffer to read from the input stream
uint8_t buf[1024];

// Read from input stream until empty, or an error;
// better error handling is left as an exercise for the reader
while (0 > [is read:buffer maxLength: sizeof buffer]) {
    SBJson4ParserStatus status = [parser parse:data];
    NSLog(@"Status: %u",status);
    // Handle parser errors here
}
[is close];

Note that you still have to read and parse the whole file to guarantee that you find a particular entry. There is no way to process just a specific entry this way.

Answer 2

I would suggest another possibility: let's suppose is messages your NSArray of dictionary object, then you can serialize it:

[[NSUserDefaults standardUserDefaults] setObject:self.messages forKey:@"com.yourdomain.messages"];
[[NSUserDefaults standardUserDefaults] synchronize];

and deserialize

self.messages = [[NSUserDefaults standardUserDefaults] arrayForKey:@"com.yourdomain.messages"];

References: Apple doc

I hope this can help you.