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I've already created a dictionary (.plist) file, and app is running. Now I want to check afterwards if an entry exists, and if not, add it. But I get stuck 'cause it's getting complicated (for me [newbie] :p). (i've simplified/cleaned up the code a bit to explain :)...)
if ([myCars indexOfObject:@\"Mercedes\"]) { NSLog(@\"yeah it is set!\"); //do nothing } else { NSLog(@\"not found\"); //how do I insert a Mercedes ????? }
I've already created a dictionary (.plist) file, and app is running. Now I want to check afterwards if an entry exists, and if not, add it. But I get stuck 'cause it's getting complicated (for me [newbie] :p). (i've simplified/cleaned up the code a bit to explain :)...)
if ([myCars indexOfObject:@\"Mercedes\"]) { NSLog(@\"yeah it is set!\"); //do nothing } else { NSLog(@\"not found\"); //how do I insert a Mercedes ????? }
You've got several issues.
First of all, when you read a data structure from a plist, everything comes back as the immutable form, even if what you wrote contained mutable objects.
Fixing that can be tricky if you have a complex structure like a dictionary that contains a dictionary that contains an array that contains dictionaries, and some or all of the internal objects need to be mutable.
Most objects that come in mutable and immutable form implement a method mutableCopy that returns a mutable version.
You could write a mutableDeepCopy method that takes a container object like an array or dictionary and traverses it to the end, and creates a mutable equivalent of all the array, dictionary, and set objects inside. It would be easier to write a mutableDeepCopy method for your specific structure than a general-purpose one, but a general-purpose method would be more useful.
Once you solve that problem, you need to figure out how to find an entry in your array that has the "make" value you are looking for.
You could do that with the NSDictionary method indexOfObjectPassingTest:
(Disclaimer: I struggle with the syntax for blocks that take parameters. I think I got the syntax above correct, but I did not compile it, much less test it.)
Assuming it works, the code above uses one of the new block-based array methods, indexOfObjectPassingTest. It takes a block of code that is run on each element in the array. That code looks at each element to see if it matches your search criteria (That it contains a make key, and the value of that key is "Mercedes"). When it finds such an element, the block returns YES, and the indexOfObjectPassingTest returns the index of the object in question.
Regards,
Duncan C WareTo
Animated GIF created with Face Dancer, available for free in the app store.
According to your plist, you have a dictionary which contains a single array which contains several dictionaries. Presumably you have successfully pulled the single array out of the parent dictionary. However, arrays are not key-value coded. The reason that your call to 'indexOfObject' is not behaving as expected is because the method tests each object in the array for equality to the argument you supply. So, your code is comparing a string (@"Mercedes") to a dictionary.
You will need to iterate through the array and test each dictionary object independently. So, iterate through the array, get the value associated with the "make" key for each dictionary, and test for equality to your string. You could also use a predicate but start with this.
altaphista
Posts: 2New Users
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First of all, when you read a data structure from a plist, everything comes back as the immutable form, even if what you wrote contained mutable objects.
Fixing that can be tricky if you have a complex structure like a dictionary that contains a dictionary that contains an array that contains dictionaries, and some or all of the internal objects need to be mutable.
Most objects that come in mutable and immutable form implement a method mutableCopy that returns a mutable version.
You could write a mutableDeepCopy method that takes a container object like an array or dictionary and traverses it to the end, and creates a mutable equivalent of all the array, dictionary, and set objects inside. It would be easier to write a mutableDeepCopy method for your specific structure than a general-purpose one, but a general-purpose method would be more useful.
Once you solve that problem, you need to figure out how to find an entry in your array that has the "make" value you are looking for.
You could do that with the NSDictionary method indexOfObjectPassingTest:
Something like this:
(Disclaimer: I struggle with the syntax for blocks that take parameters. I think I got the syntax above correct, but I did not compile it, much less test it.)
Assuming it works, the code above uses one of the new block-based array methods, indexOfObjectPassingTest. It takes a block of code that is run on each element in the array. That code looks at each element to see if it matches your search criteria (That it contains a make key, and the value of that key is "Mercedes"). When it finds such an element, the block returns YES, and the indexOfObjectPassingTest returns the index of the object in question.
Duncan C
WareTo
Animated GIF created with Face Dancer, available for free in the app store.
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0 • Off Topic Insightful Disagree Dislike Like AwesomeYou will need to iterate through the array and test each dictionary object independently. So, iterate through the array, get the value associated with the "make" key for each dictionary, and test for equality to your string. You could also use a predicate but start with this.
Here's Apple's documentation on using collections such as arrays and dictionaries: https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Collections/Collections.html#//apple_ref/doc/uid/10000034-BBCFIHFH
Good luck!
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0 • Off Topic Insightful Disagree Dislike Like Awesome@Fstuff, thanks for your reply, but can you help me with a start of code, i am quite new to obj-c.
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