As the iPad app I am making has been growing its size, it is hard for me to keep track of UI design values. Here, I am talking about values such as a table's width, background colors, and a title's font.
I would like to organize all UI design-related values and objects more efficiently.
How do you organize these?
Do you #define values in a header file?
Do you declare them as global variables or not?
Do you put your values one static class?
Or do you think not-organizing these values is rather better?
I would like to hear your advice.
Thank you :)
Yes it depends, therefore just some rules of thumb...
Do you #define values in a header file?
...in cases where I might want to change this locally only, eg for constants, colors, alignments, button images, ... the main reason why I do this however is the documentation it allows by giving the local defines a long explaining name
Do you declare them as global variables or not?
...an all my apps I have a MainDataManager Class, that holds all the variables I need globally - for the UI part often I have my own globally used object. This is extremely useful, simplifies the code, and probably one of the most important things I learned early on. might also see here Using Variable of AppDelegate as a Global Variable - question regarding release/retain
Do you put your values one static class?
...static classes exist kind of conceptually. Static variables are quite useful when you want to give a method some kind of memory of its own. However, none plays an important role in my UI.
In general, I like to use IB to layout the screens but set all the button names, labels, texts in the code. Why? Because when I have to localize the app maintaining multiple XIB files (for each language there will be one isolated XIB file to maintain) becomes a real burden even if there is only one single change in the layout.
All the global constant settings are always kept in GloblDefinitions.h while at the same time I have in my .pch file this entry #import "GlobalDefinitions.h"
So the combintation of a delegate variable provided globally + GlobalDefinitions.h for constants is my solution.
Its a good question. When combining use of interface builder with hand-coded UI tweaks and/or custom components you also have the problem of duplicated values between IB and code.
In some situations, for readability and for easy adjustment by a third party its easier if values are just hard coded in-place - so in trival cases (e.g. cases where the value is not repeated anywhere else or is unlikely to change) this might be a valid option.
In general, if the constants are specific to the layout of a particular UI component then it seems to make sense to #define them in the header file for the UI component that uses them - I think putting them all in one global file breaks the decoupling that you'd like to have between user interface components, and also for readability it can be easier for another dev to find them in the header file.
On the other hand if there are values that are used consistently across multiple UI components within the one application, then these can be defined in a global include file. Similarly if there are 'base' values that are used to derive other lengths etc. that are used commonly across multiple UI components these also can be stored in a global include.
Also whereever possible make use of the layout manager margin flexibility settings and width/height flexibility settings to minimise the need to hard code values. And when relevant, derive values from a base value or a system value (e.g. screen width).
At the end of the day if the value is there in code in front of you sometimes that much easier to figure out and tweak than changing a #define off in some other file - on the other hand - if the same value is repeated in multiple places and a #define is not used, then it can be very confusing for another coder to come in and change one of these repeated values only and try to understand and sift through the resultant side effects and which other places the value should be changed.
Well Ryan that depends upon you..
You can either use pre processor directives..
declaring in .pch file.
or you can either make an object class taking all the constants....
Hope that will help you..
Thanks
This is what I have learnt from few of my previous projects.
1] Naming conventions - use appropriate and standardized prefix. ex tblRecordLis, viewControlPanel etc.
2] Keep Constants together - keeping all constants at one place reduces the pain of searching entire project to find/fix/replace constants and their values.
3] Grouping relevant Classes together according to utility and their functionality.
4] UI constants like size, offsets , frame values (Which you need to hard code) can be kept in constants
a few which I used are
#define MenuPopoverFrame CGSizeMake(278, 550);
#define LandscapeContentSize #"{{0,0},{719,734}}"
#define PortraitContentSize #"{{2,0},{765,980}}"
5] Using IB as much as possible as it gives us more flexibility.
6] PROPER commenting and documentation proves to be a life saver when dealing with debugging.
I find it easy to declare keys as constants as using them at multiple places also increases the chances of error if used as such. eq key named #"method" can be better declared as
#define kMethodKey #"method"
This very simple thing saves my time while debugging when the project size grows larger.
** Taking hints from Apple's samples also gives you a great help in keeping your code standardized.
Related
I'm struggling with the size of output files for large Modelica models. Off course, I can protect some objects in order to remove them completely from the result file. However, that gives rise to two problems:
it's not possible to redeclare protected objects
if i want to test my model in detail (eg for a short time period), i need to declare those objects publicly again in order to see their variables
I wonder if there's a trick to set the 'verbosity' of a Modelica model. Maybe what I would like is a third keyword next to public, protected, eg. transparent. Then, when setting up a simulation, I want be able to set the verbosity level to 1, or 2 with the following effect:
1--> consider all transparentelements as protected
2--> consider all transparentelements as public
This effect would propagate to all models and submodels.
I don't think this already exists. But is there an easy workaround?
Thanks,
Roel
As Michael Tiller wrote above, this is not handled the same way in all Modelica tools and there is no definite answer. To give an OpenModelica-specific answer, it's possible to use simulate(ModelName,outputFilter="regex"), to store only the variables that fully match the given regex (default is .*, matching any variable).
Roel,
I know several people wrestling with this issue. At the moment, all of this depends on the tool being used. I don't know how other tools handle filtering of results, but in Dymola you control it (as you point out) by giving the signals special qualifiers (e.g. protected).
One thing I've done in the past is to extend from a model and then add a bunch of output signals for things I'm interested in. Then you can select "Outputs" in Dymola to make sure those get in the results file. This is far from perfect because a) listing everything you want can get tedious and b) referencing protected variables is not strictly allowed (although Dymola lets you get away with it but issues a warning).
At Dassault, we are actively discussing this idea and hope to provide some better functionality along these lines. It isn't clear whether such functionality will be strictly tool specific or whether it will involve the language somehow. But if it is language related, we will (of course) work with the design group to formulate a specification that other tool vendors can support as well.
In SystemModeler, you go to the Settings tab in the Experiment Browswer in Simulation Center. Click on Output on the bottom and select which variables to store.
(The options are state variables, derivatives, algebraic variables, parameters, protected variables and if you mark the Store simulation log-option, you'll get some interesting statistics on events over time and function evaluations, opening another possibility to track down parts of the simulation and model that creates more evaluations)
I am not sure if this helps you, but in Dymola you can go to Simulation->Setup->Output and mark a checkbox saying "Store Protected variables". That way it is possible to declare most variables as protected: during normal simulation they are not stored, but when debugging your model, you just mark that checkbox and they are stored.
Of course that is not the same as your suggested keyword transparent, but maybe it helps a little...
A bit late, but in Dymola 2013 FD01 and later you can select which variables to store based on names (and model names) using the annotation __Dymola_selections, and even filter on user-defined tags - so you could create a tag name "transparent" in the model. See "Matching and variable selections" in the manual.
This is a general design question not relating to any language. I'm a bit torn between going for minimum code or optimum organization.
I'll use my current project as an example. I have a bunch of tabs on a form that perform different functions. Lets say Tab 1 reads in a file with a specific layout, tab 2 exports a file to a specific location, etc. The problem I'm running into now is that I need these tabs to do something slightly different based on the contents of a variable. If it contains a 1 I may need to use Layout A and perform some extra concatenation, if it contains a 2 I may need to use Layout B and do no concatenation but add two integer fields, etc. There could be 10+ codes that I will be looking at.
Is it more preferable to create an individual path for each code early on, or attempt to create a single path that branches out only when absolutely required.
Creating an individual path for each code would allow my code to be extremely easy to follow at a glance, which in turn will help me out later on down the road when debugging or making changes. The downside to this is that I will increase the amount of code written by calling some of the same functions in multiple places (for example, steps 3, 5, and 9 for every single code may be exactly the same.
Creating a single path that would branch out only when required will be a bit messier and more difficult to follow at a glance, but I would create less code by placing conditionals only at steps that are unique.
I realize that this may be a case-by-case decision, but in general, if you were handed a previously built program to work on, which would you prefer?
Edit: I've drawn some simple images to help express it. Codes 1/2/3 are the variables and the lines under them represent the paths they would take. All of these steps need to be performed in a linear chronological fashion, so there would be a function to essentially just call other functions in the proper order.
Different Paths
Single Path
Creating a single path that would
branch out only when required will be
a bit messier and more difficult to
follow at a glance, but I would create
less code by placing conditionals only
at steps that are unique.
Im not buying this statement. There is a level of finesse when deciding when to write new functions. Functions should be as simple and reusable as possible (but no simpler). The correct answer is almost never 'one big file that does a lot of branching'.
Less LOC (lines of code) should not be the goal. Readability and maintainability should be the goal. When you create functions, the names should be self documenting. If you have a large block of code, it is good to do something like
function doSomethingComplicated() {
stepOne();
stepTwo();
// and so on
}
where the function names are self documenting. Not only will the code be more readable, you will make it easier to unit test each segment of the code in isolation.
For the case where you will have a lot of methods that call the same exact methods, you can use good OO design and design patterns to minimize the number of functions that do the same thing. This is in reference to your statement "The downside to this is that I will increase the amount of code written by calling some of the same functions in multiple places (for example, steps 3, 5, and 9 for every single code may be exactly the same."
The biggest danger in starting with one big block of code is that it will never actually get refactored into smaller units. Just start down the right path to begin with....
EDIT --
for your picture, I would create a base-class with all of the common methods that are used. The base class would be abstract, with an abstract method. Subclasses would implement the abstract method and use the common functions they need. Of course, replace 'abstract' with whatever your language of choice provides.
You should always err on the side of generalization, with the only exception being early prototyping (where throughput of generating working stuff is majorly impacted by designing correct abstractions/generalizations). having said that, you should NEVER leave that mess of non-generalized cloned branches past the early prototype stage, as it leads to messy hard to maintain code (if you are doing almost the same thing 3 different times, and need to change that thing, you're almost sure to forget to change 1 out of 3).
Again it's hard to specifically answer such an open ended question, but I believe you don't have to sacrifice one for the other.
OOP techniques solves this issue by allowing you to encapsulate the reusable portions of your code and generate child classes to handle object specific behaviors.
Personally I think you might (if possible by your API) create inherited forms, create them on fly on master form (with tabs), pass agruments and embed in tab container.
When to inherit form and when to decide to use arguments (code) to show/hide/add/remove functionality is up to you, yet master form should contain only decisions and argument passing and embeddable forms just plain functionality - this way you can separate organisation from implementation.
In my iPhone development, I've always used global variables for lots of stuff. The style guide in my new job says we should use context parameters instead. So I need to figure out what that means and how to do that.
Can anyone explain in more detail what this means -- or point me to some code that works this way?
Thanks
It sounds like there may be a clash in nomenclature. From this definition of Context Parameters, they seem to be concerned storing global state for the duration of a session. Perhaps, you could use a 'contextParameters' NSDictionary within NSUserDefaults to store your globals. To the extent that your globals might need to be exported in their entirety (for debugging, for state saving) this might be useful in the long run.
The style guide might just be generically saying to keep your variables scoped based on the context of their usage. For example if you have a variable that you need for the lifetime of a class instance then make it a member variable of that class. If it is something that you need for the lifetime of the app then put it in an application wide object (but not a global variable).
If you use a global object (which could mostly be a big C struct containing all your former global variables) instead of individual naked global variables, you might be able to copy the object, serialize it to save it or create a unified core dump, eventually add setters/listeners, etc.
If you break the global object up, based on the shared scope or the required context of groupings of instance/struct variables, then the fractional objects might end up being good candidates for the M portion of an MVC repartitioning of your code for better reuse, extensibility, etc.
When we should use global variable and when class variable and why?
I hope your experiences and ideas to share with us who are novice in this platform.
Example:
Let, i need to trace timestamp and position of touch events (eg. touch start, end) on a layer. I can trace it using global variable or class variable of the class which implements touch event. What should I do?
Regards,
-Sadat
This isn't a problem specific to Objective C or the iPad family of devices.
Variables should have the minimum "visibility" and "duration" that they need, and no more.
You would have to come up with some very convincing reasons for trying to get a global variable through our code review processes. They're almost always able to be replaced with something a little more appropriate.
In response to your comment:
I don't know how global/class variable affects on memory.
There's a nice snippet over here which details how to do class level variables. These are normal C file-scoped variables so they're not visible outside the file but you only get one for the class, not one for every object that you instantiate.
In that sense, they have the advantages of a global (minimal storage and the value is still accessible for reading) without the disadvantages (polluting the global name-space and making it possible for code outside of the class to change it).
And, if it doesn't need to be read outside of the file, just don't provide the initCount method.
It's kind of a flip answer, but don't use global variables at all - stick with class methods and expected encapsulation. Anything else and you'll be fighting the cocoa libraries from dusk to dawn. If you follow their patterns, which include class methods, encapsulation, delegation, etc - you'll be making huge headway with relatively little effort.
The only place where I might think to call something a "global variable" in my efforts are project-wide constants - so not variables at all, but sometimes there's a good need for a constant across your project (TableViewCell identifiers comes to mind)
I want to create a big file for all cool functions I find somehow reusable and useful, and put them all into that single file. Well, for the beginning I don't have many, so it's not worth thinking much about making several files, I guess. I would use pragma marks to separate them visually.
But the question: Would those unused methods bother in any way? Would my application explode or have less performance? Or is the compiler / linker clever enough to know that function A and B are not needed, and thus does not copy their "code" into my resulting app?
This sounds like an absolute architectural and maintenance nightmare. As a matter of practice, you should never make a huge blob file with a random set of methods you find useful. Add the methods to the appropriate classes or categories. See here for information on the blob anti-pattern, which is what you are doing here.
To directly answer your question: no, methods that are never called will not affect the performance of your app.
No, they won't directly affect your app. Keep in mind though, all that unused code is going to make your functions file harder to read and maintain. Plus, writing functions you're not actually using at the moment makes it easy to introduce bugs that aren't going to become apparent until much later on when you start using those functions, which can be very confusing because you've forgotten how they're written and will probably assume they're correct because you haven't touched them in so long.
Also, in an object oriented language like Objective-C global functions should really only be used for exceptional, very reusable cases. In most instances, you should be writing methods in classes instead. I might have one or two global functions in my apps, usually related to debugging, but typically nothing else.
So no, it's not going to hurt anything, but I'd still avoid it and focus on writing the code you need now, at this very moment.
The code would still be compiled and linked into the project, it just wouldn't be used by your code, meaning your resultant executable will be larger.
I'd probably split the functions into seperate files, depending on the common areas they are to address, so I'd have a library of image functions separate from a library of string manipulation functions, then include whichever are pertinent to the project in hand.
I don't think having unused functions in the .h file will hurt you in any way. If you compile all the corresponding .m files containing the unused functions in your build target, then you will end up making a bigger executable than is required. Same goes for if you include the code via static libraries.
If you do use a function but you didn't include the right .m file or library, then you'll get a link error.