Question

My application uses NSTask to start a Python script, then the script returns an array via NSPipe. I read the data, stick it in a string, and display it:

NSMutableData *data = [[NSMutableData alloc] init];
NSData *readData;

while ((readData = [readHandle availableData])&& [readData length]) {
    [data appendData: readData];
}


NSString *string = [[NSString alloc] 
                    initWithData: data 
                    encoding: NSUTF8StringEncoding];

That’s all fine, but I realized I really need to keep it as an array – not a string. I can’t find a method that initiates array from data (data returned from NSPipe). How can I do that? The closest thing I found is possibly using:

[NSPropertyListSerialization dataWithPropertyList:format:options:error:]

… but I don’t need a “property list” per se. Do I have to convert the data to plist first?

EDITED: I just realized it’s more complicated than I thought. Python returns an array of dictionaries, in the dictionary there are strings. These strings can have commas and other chars, so I don’t think I can use a “,” separator to break it up.

in Python:

msg_set = []
msg_set = [
   dict(mts="t,s1", mfrom="f@ro,m1", msbj="msb,j1", mbody="bod,y1", mid="i,d1"),
   dict(mts="ts2", mfrom="from2", msbj="msb,j2", mbody="body2", mid="id2")
]
print msg_set # <- this is what python returns

Answer 1

You can convert the data to JSON first (I saw the comments on dasblinkenlight’s answer but I had already typed my answer) and then pass them to Cocoa. Something like this:

Python Side

import json
#...
json.dumps(msg_set) # <- return this one instead

Objective-C Side

NSString *myPythonJson = @""; // <- Whatever you got from python
NSError *error = nil;
id myObjectsFromJson = [NSJSONSerialization JSONObjectWithData:[myPythonJson dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingAllowFragments error:&error];