QT based software framework design

1、 Introduction
Qt, In the understanding of many people, it is a framework for making interfaces , Only used for interface , The back end is often implemented by others . In my practice , I use both interface and back-end implementation Qt To implement the .

2、 Software layering
Generally speaking , Our software architecture will be very layered , Here we have three floors 了 , The layering is shown in the figure below ：

 

2.1 GUI layer
Here we are based on Qt Of , So this layer is used Qt Class library to achieve , All the main interfaces will be from these three classes ：QWiget,QMainWindow,QDialog One of them inherits , And in main Generate an instance in the function and show come out , Enter the main message loop . I am used to using QWiget, Don't use UI file , All interfaces are new come out , Then use code to layout .

2.2 Models layer
model Layer mainly realizes the business logic of our software , The modules here are reasonably divided according to the business logic of the whole software , Achieve the effect of high cohesion and loose coupling . Here we are concerned with one of these business logic classes , There? new There is a problem . Here's what I did ： Make one bridge class , Let all business logic classes be in this bridge Instantiate in class .

2.3 Communication layer
In this layer, data collection is realized , signal communication The way There are many kinds , Serial port , There is a net port , Yes CAN Mouth, etc . The data received by this layer is sent to models Layer hair , User input is also sent to the actuator through this layer .

So this layer of classes , Where to instantiate ？ I also choose bridge In class , such ,bridge Class is actually a class without any business functions , It only provides that various classes can interact with each other connect（ Signal slot ） The carrier of .

3、 Lower floor and GUI Communication at the management level
thus , Our division GUI Class of layer （ Communication and module ） All in bridge Classes can communicate through the mechanism of signal slots . So how does our model match GUI To communicate ？

We can go through this bridge Class , Because of our other All classes are in bridge Class , So this class can have class references , We can do it in QWidget Pass a constructor in bridge Class pointer goes in , such , All our classes , Can be with GUI We're communicating .

4、 Run the architecture
When we have designed all levels of code , And know in that category , After that level is realized , We need to use threads to make the whole software run happily . This is what we want to say about the operation architecture .

generally speaking , We put all the communication All classes Will come out alone as a thread , such , It won't block GUI Threads , It can also respond faster to collect information and transmit control information to the lower computer .

therefore communication This floor , Generally, there are several threads in several ports . Of course, some lightweight ones can be combined in one thread .

bridge Class received GUI In the thread , Why do that , When our interface pops up , From you to model in get The latest value is displayed on the interface ,（ It is also possible to use signal slots, but it will be more cumbersome ）, So call get Methods , There is such a need , We'd better put all model All in one thread ——- namely GUI Threads .

In this way, the main framework of our small information acquisition and control system is built .

The last point to emphasize is ： Recommended when using threads movetothread Methods . If you don't use this method , All instances must be in the thread run() In the function new come out , To ensure that the slot function of this class is executed in the message loop of this thread .
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