4 ms·

You're right, delete is an instance method. You call it like so: [myObject delete]; So the object referred to by the variable myObject gets deleted from our se

You're right, delete is an instance method. You call it like so: [myObject delete]; So the object referred to by the variable myObject gets deleted from our servers. It was created whenever it was instantiated using a query. What global is it using? saveAll is a static (class) method. It takes in a collection of instantiated objects and saves them to our servers. What global is it using? As for interjecting custom behavior, perhaps you're missing that all of these methods take in a variety of callbacks that can modify behavior.

nupark2 15y ago
So the object referred to by the variable myObject gets deleted from our servers. It was created whenever it was instantiated using a query. What global is it using? How does myObject acquire a reference of some kind to your servers, and the context in which it is stored? (That's the answer). saveAll is a static (class) method. It takes in a collection of instantiated objects and saves them to our servers. What global is it using? As for interjecting custom behavior, perhaps you're missing that all of these methods take in a variety of callbacks that can modify behavior. How do I arbitrarily modify the saveAll method so that I can perform arbitrary operations on objects before they're saved, so that I can implement a custom undo manager (but only when working on objects in the context of the user editing the document. Elsewhere I want different behavior)? ---- These approaches (class methods, singletons/globals) are breaking OO polymorphism, and significantly hamstringing your APIs. I'll try to provide an example that might matter to you: Let's pretend that I want to add support for sharing data between users of my application. It's important to me to not repeat myself, so I want to have the same code be able to write data to the user's personal storage, write data to one of several possible shared storage destinations. You decide you want to support this API. How do you make your current global/singleton API work for me?
- csmajorfive 15y ago
  The hostname of our servers is indeed hardcoded in the framework. So, yes, that's a 'singleton' in the same way that configuring your database hostname in Rails is a singleton. So far our developers have had a lot of success building upon Parse. There are certainly some missing pieces (like the one pointed out in another comment on this post) but none of them have related to our overall architecture. I invite you to let us know what it should look like ideally at founders@parse.com or even stop by our office. We love to talk with developers.
  - nupark2 15y ago
    The hostname of our servers is indeed hardcoded in the framework. So, yes, that's a 'singleton' in the same way that configuring your database hostname in Rails is a singleton. I get the impression that arguing this further is a dead end. I'd suggest looking at NSManagedObjectContext for a basic approach that doesn't rely on global state / global variables, and while imperfect in many ways, is at least familiar to existing ObjC developers. Lastly, I'd look into the research into the effects of global variables on program interdependence, as well as the numerous discussions on the negative impact on maintainability, composability. Regardless of the above, it sounds like Parse will likely not be a good fit for our (large, complex, and top-chart) applications. If we're not the target audience, then no problem.
    - lacker 15y ago
      We did look at NSManagedObjectContext... but NSManagedObjectContext doesn't support polymorphism. http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObjectContext_Class/NSManagedObjectContext.html http://developer.apple.com/library/mac/#documentation/Cocoa/... You are strongly discouraged from subclassing NSManagedObjectContext. The change tracking and undo management mechanisms are highly optimized and hence intricate and delicate. Interposing your own additional logic that might impact processPendingChanges can have unforeseen consequences.
      - nupark2 15y ago
        We did look at NSManagedObjectContext... but NSManagedObjectContext doesn't support polymorphism. Yes, it does. For a few reasons: 1) It is passed around as an instance, not a global variable, and as such, each instance can be individually configured to behave differently (such as with a different persistence implementation), while still responding to defined API. 2) NSManagedObjectContext can be subclassed. 3) Apple can improve the implementation (and recommend subclassing in the future) without breaking or modifying any existing client code. You're confusing 'polymorphism' with subclassing. Related, but not the same. --- Now, I did say that NSManagedObjectContext has many flaws -- and it does, but they're largely unrelated to the use of global variables that we're addressing here. And, since I'm being downvoted for technical discussion (presumably by you guys or your friends, because I've never seen anything like this to comments like mine on hacker news), I'm going to respond personally: Your need to find (and listen to) an advisor who has a significant stake in the ObjC space and more experience with API design than you have. You appear to be approaching your API from a Rails-centric perspective, not one rooted in Objective-C application development experience, and certainly not one rooted in the experience of architecting large shipping desktop/mobile applications. Then again, maybe your target audience are just small throw-away apps, in which case your API is probably fine -- just about any API would be.

nupark2 15y ago

So the object referred to by the variable myObject gets deleted from our servers. It was created whenever it was instantiated using a query. What global is it using? How does myObject acquire a reference of some kind to your servers, and the context in which it is stored? (That's the answer). saveAll is a static (class) method. It takes in a collection of instantiated objects and saves them to our servers. What global is it using? As for interjecting custom behavior, perhaps you're missing that all of these methods take in a variety of callbacks that can modify behavior. How do I arbitrarily modify the saveAll method so that I can perform arbitrary operations on objects before they're saved, so that I can implement a custom undo manager (but only when working on objects in the context of the user editing the document. Elsewhere I want different behavior)? ---- These approaches (class methods, singletons/globals) are breaking OO polymorphism, and significantly hamstringing your APIs. I'll try to provide an example that might matter to you: Let's pretend that I want to add support for sharing data between users of my application. It's important to me to not repeat myself, so I want to have the same code be able to write data to the user's personal storage, write data to one of several possible shared storage destinations. You decide you want to support this API. How do you make your current global/singleton API work for me?

csmajorfive 15y ago
The hostname of our servers is indeed hardcoded in the framework. So, yes, that's a 'singleton' in the same way that configuring your database hostname in Rails is a singleton. So far our developers have had a lot of success building upon Parse. There are certainly some missing pieces (like the one pointed out in another comment on this post) but none of them have related to our overall architecture. I invite you to let us know what it should look like ideally at founders@parse.com or even stop by our office. We love to talk with developers.
- nupark2 15y ago
  The hostname of our servers is indeed hardcoded in the framework. So, yes, that's a 'singleton' in the same way that configuring your database hostname in Rails is a singleton. I get the impression that arguing this further is a dead end. I'd suggest looking at NSManagedObjectContext for a basic approach that doesn't rely on global state / global variables, and while imperfect in many ways, is at least familiar to existing ObjC developers. Lastly, I'd look into the research into the effects of global variables on program interdependence, as well as the numerous discussions on the negative impact on maintainability, composability. Regardless of the above, it sounds like Parse will likely not be a good fit for our (large, complex, and top-chart) applications. If we're not the target audience, then no problem.
  - lacker 15y ago
    We did look at NSManagedObjectContext... but NSManagedObjectContext doesn't support polymorphism. http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/CoreDataFramework/Classes/NSManagedObjectContext_Class/NSManagedObjectContext.html http://developer.apple.com/library/mac/#documentation/Cocoa/... You are strongly discouraged from subclassing NSManagedObjectContext. The change tracking and undo management mechanisms are highly optimized and hence intricate and delicate. Interposing your own additional logic that might impact processPendingChanges can have unforeseen consequences.
    - nupark2 15y ago
      We did look at NSManagedObjectContext... but NSManagedObjectContext doesn't support polymorphism. Yes, it does. For a few reasons: 1) It is passed around as an instance, not a global variable, and as such, each instance can be individually configured to behave differently (such as with a different persistence implementation), while still responding to defined API. 2) NSManagedObjectContext can be subclassed. 3) Apple can improve the implementation (and recommend subclassing in the future) without breaking or modifying any existing client code. You're confusing 'polymorphism' with subclassing. Related, but not the same. --- Now, I did say that NSManagedObjectContext has many flaws -- and it does, but they're largely unrelated to the use of global variables that we're addressing here. And, since I'm being downvoted for technical discussion (presumably by you guys or your friends, because I've never seen anything like this to comments like mine on hacker news), I'm going to respond personally: Your need to find (and listen to) an advisor who has a significant stake in the ObjC space and more experience with API design than you have. You appear to be approaching your API from a Rails-centric perspective, not one rooted in Objective-C application development experience, and certainly not one rooted in the experience of architecting large shipping desktop/mobile applications. Then again, maybe your target audience are just small throw-away apps, in which case your API is probably fine -- just about any API would be.