4 ms·

I really despised having to use moc for QT and I'm glad to have found this, it works quite well. Needs C++14 though.

Nicksil 7y ago
I'm interested in hearing your thoughts on the MOC if you have time and don't mind sharing. I've been researching QT's software design approach, architecture, etc. ("core" code base in general), and stand to benefit from learning the pros and cons of software built this way.
- ailideex 7y ago
  My biggest gripe with MOC is that it makes it no longer C++ and if I just want to quickly throw together some sample code and build it with a makefile I can't. This still requires the use of a separate header file with is annoying but a lot less annoying than writing in a language which is not c++ and which does not work with a simple toolchain.
  - jcelerier 7y ago
    You don't need a separate header, you can just do #include "foo.moc" at the end. I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h).
    - inetknght 7y ago
      > I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h). It's been a while since I've used Qt but if I recall correctly MOC also parsed and read the user interface files to generate the headers which get included in the C++ source.
      - simion314 7y ago
        You are not forced to use the designer tool, you can build the GUI with C++ directly if you need that for some reason.
        slavik81 7y ago
        There's also a stand-alone designer you can use on individual ui files. In general, there's no need to have the whole project in Qt Creator just to edit a ui file. You can also edit the ui files in a normal text editor. They're just XML files that specify the widget hierarchy to construct. If you have a few example files to work from, they're pretty straight-forward to understand and modify. Validating your changes using designer is definitely faster than recompiling your program, but it's an option.
      - blattimwind 7y ago
        No, that's what uic does.
    - ailideex 7y ago
      > You don't need a separate header, you can just do #include "foo.moc" at the end. I was talking about verdigris for which you have to do #include "wobjectimpl.h" > I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h). If it was pure C++ then I would not need to run a MOC to generate working executables. While they are also plain CPP macros they have semantics which is only understood by the MOC and is not captured by CPP or C++. This additional semantics is the reason why they are used in the first place because if it was not for the additional semantics again you would not need MOC.
      - johannes1234321 7y ago
        All my types (and `#define`s) have some semantic meaning only I and non of my tools understand. It is nice if a tool understands those and for an `emit` suggests only my signals for auto-completion, but if it lists them along all other members it is fine. So I can see the argument from a puristic view, but in practice, once my built is setup to run it (cmake automoc or something), it simply works. My issue with Qt is that the API design comes from days very long ago, where they did fantastic work on keeping compatibility, while not adopting to "modern C++" which always requires me to rethink the way I write code. Also integrating with non-Qt code isn't always easy due to reliance on QString (which has value Unicode features), QList (which meanwhile has many std-like APIs) etc. which easily travel through all layers. Thus when staying inside At it's really nice and quite consistent, but integrating is hard.
        ailideex 7y ago
        > All my types (and `#define`s) have some semantic meaning only I and non of my tools understand. If it is not semantics essential to the correct operation of your program then this is a different matter. I really am not sure what the contention here or misunderstanding is. When I write C++ I write it for a C pre-processor and C++ compiler to read in order to obtain a output program which does something specific and in line with the C++ standard. This is not some high minded purism - this is just pragmatic reality. If I write something in my source which I expect to result in specific output but the specific output cannot be obtained if I use a standard compliant C Preprosessor and C++ Compiler then either my expectation is wrong or I'm writing something which is not C++. So if you don't rely on the behaviour that results from MOC being part of the toolchain then sure - you are writing C++ - if you do - it is not C++. If the semantics (in a sense where it actually affects output) is part of a language, which it is, then changing the semantics of the language makes it a different language. > So I can see the argument from a puristic view, but in practice, once my built is setup to run it (cmake automoc or something), it simply works. This does not make it C++.
- gpderetta 7y ago
  I do not have much experience with Qt, but moc is one of those things that seems a bog deal in theory (it os not c++, what's the debugging experience, what happens if it breaks) but it is absolutely not an issue in practice (you forget it exists very quickly).
blattimwind 7y ago
"despised" does not sound like a rational thing.
- billfruit 7y ago
  My thinking was why require an intermediate processing step of the moc, if the core c++ is capable enough. Other toolkits like gtk does not seem to require intermediate compilation step too. Also the QObject stuff added by qt is quite mysterious atleast on the first look. Also using the moc is a bit similar to using complex preprocessor-macr-ridden c code, which to me is an antipattern.
  - jcelerier 7y ago
    > My thinking was why require an intermediate processing step of the moc, if the core c++ is capable enough. Sadly it is not. C++ does not provide reflection - not without macros duplicating all your function names. GTK+ does not provide reflection. For instance with Qt you can just define a C++ object and directly access its properties & methods from Javascript, which is extremely useful if you want to add a scripting layer to an existing software. You can also iterate over all the properties of an object to create UIs automatically.
  - ogoffart 7y ago
    Gtk uses GLib which basically re-invent object oriented programming with "complex preprocessor-macr-ridden c code" boilerplate. I find moc approach much superior to that as it just help the programmer concentrate on what to program without having to manually write all the error-prone boilerplate. Qt makes UI programming in C++ easier, nothing wrong that.
  - blattimwind 7y ago
    > Also using the moc is a bit similar to using complex preprocessor-macr-ridden c code, which to me is an antipattern. We sort of agree. gobject is a "kill it with fire" kind of mess, moc is not exactly the pinnacle of elegance either (but does more than glib gives you and somehow manages to be less weird than glib's macro jungle). The basic fact is that moc works around C++ not being able to provide this kind of functionality; so either you take some inconvenience (gtk, verdigris) or use an external tool (moc). moc doesn't usually give any trouble beyond being somewhat slow, so that seems like an acceptable deal for almost any situations you might consider using Qt in.

I'm interested in hearing your thoughts on the MOC if you have time and don't mind sharing. I've been researching QT's software design approach, architecture, etc. ("core" code base in general), and stand to benefit from learning the pros and cons of software built this way.

ailideex 7y ago
My biggest gripe with MOC is that it makes it no longer C++ and if I just want to quickly throw together some sample code and build it with a makefile I can't. This still requires the use of a separate header file with is annoying but a lot less annoying than writing in a language which is not c++ and which does not work with a simple toolchain.
- jcelerier 7y ago
  You don't need a separate header, you can just do #include "foo.moc" at the end. I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h).
  - inetknght 7y ago
    > I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h). It's been a while since I've used Qt but if I recall correctly MOC also parsed and read the user interface files to generate the headers which get included in the C++ source.
    - simion314 7y ago
      You are not forced to use the designer tool, you can build the GUI with C++ directly if you need that for some reason.
      - slavik81 7y ago
        There's also a stand-alone designer you can use on individual ui files. In general, there's no need to have the whole project in Qt Creator just to edit a ui file. You can also edit the ui files in a normal text editor. They're just XML files that specify the widget hierarchy to construct. If you have a few example files to work from, they're pretty straight-forward to understand and modify. Validating your changes using designer is definitely faster than recompiling your program, but it's an option.
    - blattimwind 7y ago
      No, that's what uic does.
  - ailideex 7y ago
    > You don't need a separate header, you can just do #include "foo.moc" at the end. I was talking about verdigris for which you have to do #include "wobjectimpl.h" > I'd be interested in knowing in which way it is no longer c++, considering Q_OBjECT, signals, slots, ... are just plain cpp macros (see qobjectdefs.h). If it was pure C++ then I would not need to run a MOC to generate working executables. While they are also plain CPP macros they have semantics which is only understood by the MOC and is not captured by CPP or C++. This additional semantics is the reason why they are used in the first place because if it was not for the additional semantics again you would not need MOC.
    - johannes1234321 7y ago
      All my types (and `#define`s) have some semantic meaning only I and non of my tools understand. It is nice if a tool understands those and for an `emit` suggests only my signals for auto-completion, but if it lists them along all other members it is fine. So I can see the argument from a puristic view, but in practice, once my built is setup to run it (cmake automoc or something), it simply works. My issue with Qt is that the API design comes from days very long ago, where they did fantastic work on keeping compatibility, while not adopting to "modern C++" which always requires me to rethink the way I write code. Also integrating with non-Qt code isn't always easy due to reliance on QString (which has value Unicode features), QList (which meanwhile has many std-like APIs) etc. which easily travel through all layers. Thus when staying inside At it's really nice and quite consistent, but integrating is hard.
      - ailideex 7y ago
        > All my types (and `#define`s) have some semantic meaning only I and non of my tools understand. If it is not semantics essential to the correct operation of your program then this is a different matter. I really am not sure what the contention here or misunderstanding is. When I write C++ I write it for a C pre-processor and C++ compiler to read in order to obtain a output program which does something specific and in line with the C++ standard. This is not some high minded purism - this is just pragmatic reality. If I write something in my source which I expect to result in specific output but the specific output cannot be obtained if I use a standard compliant C Preprosessor and C++ Compiler then either my expectation is wrong or I'm writing something which is not C++. So if you don't rely on the behaviour that results from MOC being part of the toolchain then sure - you are writing C++ - if you do - it is not C++. If the semantics (in a sense where it actually affects output) is part of a language, which it is, then changing the semantics of the language makes it a different language. > So I can see the argument from a puristic view, but in practice, once my built is setup to run it (cmake automoc or something), it simply works. This does not make it C++.
gpderetta 7y ago
I do not have much experience with Qt, but moc is one of those things that seems a bog deal in theory (it os not c++, what's the debugging experience, what happens if it breaks) but it is absolutely not an issue in practice (you forget it exists very quickly).

blattimwind 7y ago

"despised" does not sound like a rational thing.

billfruit 7y ago
My thinking was why require an intermediate processing step of the moc, if the core c++ is capable enough. Other toolkits like gtk does not seem to require intermediate compilation step too. Also the QObject stuff added by qt is quite mysterious atleast on the first look. Also using the moc is a bit similar to using complex preprocessor-macr-ridden c code, which to me is an antipattern.
- jcelerier 7y ago
  > My thinking was why require an intermediate processing step of the moc, if the core c++ is capable enough. Sadly it is not. C++ does not provide reflection - not without macros duplicating all your function names. GTK+ does not provide reflection. For instance with Qt you can just define a C++ object and directly access its properties & methods from Javascript, which is extremely useful if you want to add a scripting layer to an existing software. You can also iterate over all the properties of an object to create UIs automatically.
- ogoffart 7y ago
  Gtk uses GLib which basically re-invent object oriented programming with "complex preprocessor-macr-ridden c code" boilerplate. I find moc approach much superior to that as it just help the programmer concentrate on what to program without having to manually write all the error-prone boilerplate. Qt makes UI programming in C++ easier, nothing wrong that.
- blattimwind 7y ago
  > Also using the moc is a bit similar to using complex preprocessor-macr-ridden c code, which to me is an antipattern. We sort of agree. gobject is a "kill it with fire" kind of mess, moc is not exactly the pinnacle of elegance either (but does more than glib gives you and somehow manages to be less weird than glib's macro jungle). The basic fact is that moc works around C++ not being able to provide this kind of functionality; so either you take some inconvenience (gtk, verdigris) or use an external tool (moc). moc doesn't usually give any trouble beyond being somewhat slow, so that seems like an acceptable deal for almost any situations you might consider using Qt in.