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Given that the book talks about it being used for controller buttons and for undoable actions in strategy games and editors, performance is not a significant co

Given that the book talks about it being used for controller buttons and for undoable actions in strategy games and editors, performance is not a significant concern and event-dispatchers are insufficient. Your comment is not particularly on-topic.

gravypod 9y ago
> Given that the book talks about it being used for controller buttons and for undoable actions in strategy games and editors The state should be managed by a UI object if you're talking about calling up UIs. The key presses will be subscribed to in that object and, when the event is triggered, the UI object takes over. Then the button is clicked again the UI object can undo whatever state it has created. > performance is not a significant concern Performance isn't my concern. My concern is that you've created 6 new classes to handle 5 button clicks. That sort of class bloating makes it very difficulty to enter the code base (lots of unneeded wrappers for actions). It also decouples the action from the object that the action is built for. This spreading doesn't make sense to me. The UI object should handle all things UI. The player's object should handle all things player. A Command object shouldn't be extended by 10 other objects who all touch different objects doing different things. > event-dispatchers are insufficient Why? > Your comment is not particularly on-topic. It is. I am talking about how I only got a few pages in and found it to be promoting patterns I'd consider harmful which either use an abstraction that doesn't fit the problem, or do things that make it very hard to enter a new code base.
- ghusbands 9y ago
  As you say, you've not programmed games, and it becomes clear in your further replies. To describe the often-used Command pattern as "harmful" is somewhat obtuse. Event-dispatch does not include undo functionality, and the command pattern can itself enhance debugging. That you dislike a particular, widely used pattern in the few pages you've bothered reading of a book that's outside of your experience doesn't really help anyone interested in reading that book. That's why I described it as not particularly on-topic.
  - MereInterest 9y ago
    And in that case, the polite response would be to explain why the pattern is used, rather than attacking the OP as being off-topic. Reading and asking questions when things are not understood, as the OP did, is how one gains understanding. Saying that someone should not even ask questions unless one has experience, as you did, is how one discourages people from learning.
    - ghusbands 9y ago
      If the OP had been asking questions, I might. Instead, they were posting unfounded, authoritative, nitpicking negativity ("the Command interface wasn't a good replacement") against what looks to be a reasonably good book. I understand that blithe, negative comments tend to rise to the top on HN, so I guess it's normal.
      - gravypod 9y ago
        > unfounded, authoritative, nitpicking negativity After seeing shadowmint's reply I understand why the "Command" organization is a good idea. Like shadowmint I don't see Jump as being a good example. The examples in this book make it difficult to see why this is a good idea. If the examples of this book are taken to heart and directly applied then I think the code of the resulting game would be unwieldy. It seems the only people who understand what the author is trying to show are the ones who actually have experience in the field where they've constructed these methods of scaffolding already. If this book is directed at programmers who are not game developers yet then this book as not succeeded. As a programmer, who's spent more a quarter of their years on this Earth in the field, if I can't get the sense of why a pattern shown in this book would be useful then I think there's a problem. The book is not effectively reaching it's intended audience: programmers who are not game developers or who are new to game development paradigms. I think my point still stands. For what the example is showing the Command interface isn't an appropriate replacement for the if-else tree. I still think an Event system is a better choice for dispatching an action to handlers. It seems like real game developers also feel this way (see BatFastard's comment). > against what looks to be a reasonably good book A good book can have a few bad examples. A good book also requires many revisions. This is more so when you're talking about technical books. Do you think the first revision of the Art of Computer Programming was perfect when published? There are many hexadecimal dollars out there to show you that is not the case [1]. > I understand that blithe, negative comments tend to rise to the top on HN, so I guess it's normal. If you refuse to look at valid criticism and just go strait to saying "Oh HackerNews is so negative! That's why people are agreeing with you!" then you're going to be avoiding a treasure trove of good information out there. I've had much harsher "criticism" of my work levied in person by people I actually know and instead of putting on blinders I addressed it and ended up with a better product in the end. [1] - https://en.wikipedia.org/wiki/Knuth_reward_check https://en.wikipedia.org/wiki/Knuth_reward_check
- shadowmint 9y ago
  Yup. See, this is why I struggle to recommend this book. > In some ways, the Command pattern is a way of emulating closures in languages that don’t have them. ... > For me, the usefulness of the Command pattern really shows how effective the functional paradigm is for many problems. So close, yet so far. The Command pattern is a brilliantly useful pattern, and I've seen it used to great effect; but it's not remotely about callbacks or closures; thats just an implementation detail. You're completely right, do you really need a JumpCommand, a JumpCommandHandler, and an UndoJumpCommand (?? What does that even mean?) when you could just have one class, called Player, with a method `jump`? No. You don't. It's a daft example. The Command pattern is about have composable atomic state transactions over your game state. For example, if you have a SpawnMonsterCommand, and a ApplyStatusEffectCommand, you can create a hoard of raging monsters using a SpawnHoardCommand; that calls the SpawnMonsterCommand 100x and then calls ApplyStatusEffectCommand to the monsters. Then you can have a SpawnBattleCommand that calls SpawnHoardCommand twice, with a different faction, or say, three times with 3 different factions to generate a battle. Or perhaps you're using an async resolution model, where you're commands are like MoveToLocationCommand, and AttackTargetCommand; and you need to start the MoveToLocationCommand then wait for it to finish before you run the AttackTargetCommand. Abstracting the functionality into small chunks lets you easily build complex chained behaviour, and you can even test it easily because each 'Command' is an isolated and known behaviour. ...but yeah, totally. A flurry of classes. Don't use it if you don't get some value from it. Having an undoable 'JumpCommand' falls firmly into the 'dont bother' category.
  - gravypod 9y ago
    With that use case I can understand why people would want this! You should make one of these books.

gravypod 9y ago

> Given that the book talks about it being used for controller buttons and for undoable actions in strategy games and editors The state should be managed by a UI object if you're talking about calling up UIs. The key presses will be subscribed to in that object and, when the event is triggered, the UI object takes over. Then the button is clicked again the UI object can undo whatever state it has created. > performance is not a significant concern Performance isn't my concern. My concern is that you've created 6 new classes to handle 5 button clicks. That sort of class bloating makes it very difficulty to enter the code base (lots of unneeded wrappers for actions). It also decouples the action from the object that the action is built for. This spreading doesn't make sense to me. The UI object should handle all things UI. The player's object should handle all things player. A Command object shouldn't be extended by 10 other objects who all touch different objects doing different things. > event-dispatchers are insufficient Why? > Your comment is not particularly on-topic. It is. I am talking about how I only got a few pages in and found it to be promoting patterns I'd consider harmful which either use an abstraction that doesn't fit the problem, or do things that make it very hard to enter a new code base.

ghusbands 9y ago
As you say, you've not programmed games, and it becomes clear in your further replies. To describe the often-used Command pattern as "harmful" is somewhat obtuse. Event-dispatch does not include undo functionality, and the command pattern can itself enhance debugging. That you dislike a particular, widely used pattern in the few pages you've bothered reading of a book that's outside of your experience doesn't really help anyone interested in reading that book. That's why I described it as not particularly on-topic.
- MereInterest 9y ago
  And in that case, the polite response would be to explain why the pattern is used, rather than attacking the OP as being off-topic. Reading and asking questions when things are not understood, as the OP did, is how one gains understanding. Saying that someone should not even ask questions unless one has experience, as you did, is how one discourages people from learning.
  - ghusbands 9y ago
    If the OP had been asking questions, I might. Instead, they were posting unfounded, authoritative, nitpicking negativity ("the Command interface wasn't a good replacement") against what looks to be a reasonably good book. I understand that blithe, negative comments tend to rise to the top on HN, so I guess it's normal.
    - gravypod 9y ago
      > unfounded, authoritative, nitpicking negativity After seeing shadowmint's reply I understand why the "Command" organization is a good idea. Like shadowmint I don't see Jump as being a good example. The examples in this book make it difficult to see why this is a good idea. If the examples of this book are taken to heart and directly applied then I think the code of the resulting game would be unwieldy. It seems the only people who understand what the author is trying to show are the ones who actually have experience in the field where they've constructed these methods of scaffolding already. If this book is directed at programmers who are not game developers yet then this book as not succeeded. As a programmer, who's spent more a quarter of their years on this Earth in the field, if I can't get the sense of why a pattern shown in this book would be useful then I think there's a problem. The book is not effectively reaching it's intended audience: programmers who are not game developers or who are new to game development paradigms. I think my point still stands. For what the example is showing the Command interface isn't an appropriate replacement for the if-else tree. I still think an Event system is a better choice for dispatching an action to handlers. It seems like real game developers also feel this way (see BatFastard's comment). > against what looks to be a reasonably good book A good book can have a few bad examples. A good book also requires many revisions. This is more so when you're talking about technical books. Do you think the first revision of the Art of Computer Programming was perfect when published? There are many hexadecimal dollars out there to show you that is not the case [1]. > I understand that blithe, negative comments tend to rise to the top on HN, so I guess it's normal. If you refuse to look at valid criticism and just go strait to saying "Oh HackerNews is so negative! That's why people are agreeing with you!" then you're going to be avoiding a treasure trove of good information out there. I've had much harsher "criticism" of my work levied in person by people I actually know and instead of putting on blinders I addressed it and ended up with a better product in the end. [1] - https://en.wikipedia.org/wiki/Knuth_reward_check https://en.wikipedia.org/wiki/Knuth_reward_check
shadowmint 9y ago
Yup. See, this is why I struggle to recommend this book. > In some ways, the Command pattern is a way of emulating closures in languages that don’t have them. ... > For me, the usefulness of the Command pattern really shows how effective the functional paradigm is for many problems. So close, yet so far. The Command pattern is a brilliantly useful pattern, and I've seen it used to great effect; but it's not remotely about callbacks or closures; thats just an implementation detail. You're completely right, do you really need a JumpCommand, a JumpCommandHandler, and an UndoJumpCommand (?? What does that even mean?) when you could just have one class, called Player, with a method `jump`? No. You don't. It's a daft example. The Command pattern is about have composable atomic state transactions over your game state. For example, if you have a SpawnMonsterCommand, and a ApplyStatusEffectCommand, you can create a hoard of raging monsters using a SpawnHoardCommand; that calls the SpawnMonsterCommand 100x and then calls ApplyStatusEffectCommand to the monsters. Then you can have a SpawnBattleCommand that calls SpawnHoardCommand twice, with a different faction, or say, three times with 3 different factions to generate a battle. Or perhaps you're using an async resolution model, where you're commands are like MoveToLocationCommand, and AttackTargetCommand; and you need to start the MoveToLocationCommand then wait for it to finish before you run the AttackTargetCommand. Abstracting the functionality into small chunks lets you easily build complex chained behaviour, and you can even test it easily because each 'Command' is an isolated and known behaviour. ...but yeah, totally. A flurry of classes. Don't use it if you don't get some value from it. Having an undoable 'JumpCommand' falls firmly into the 'dont bother' category.
- gravypod 9y ago
  With that use case I can understand why people would want this! You should make one of these books.