What are the namespaces and function overloads of + and @ in front of MATLAB folder

Preface

When you open MATLAB Of toolbox Folder when ( Toolbox storage path ), You will find some strange symbols in front of the folder name ：

？？？ Inside + and @ What are the ？？？

To explore this question , We have created a folder with the following directories ：

 Current folder ──@cell──dispTest.m
        |
        ├──@double──dispTest.m
        |
        ├──+test1──+test2──test.m
        |       |
        |       └──test.m
        |
        └──untitled.m      

Namespace ： Path function ( Directory structure )

If you want the code to be tidy , In many cases, some tool functions of the same kind will be placed in a separate folder , That is, the function you want to call is in a folder in the current folder , You cannot call this function directly in the current folder , What should I do ？

Many people will choose direct addpath, But in this case, those tool functions can be called by more than the project , Other items in other locations can also call , This may lead to naming conflicts .

Then a very simple method is to name the folder where the tool functions are installed +fordername In the form of , There is a + In the form of , In fact, the folder path is used as the namespace .

For the following parts of the catalog we proposed earlier ：

 Current folder ──+test1──+test2──test.m
        |       |
        |       └──test.m
        |
        └──untitled.m   

I want to untitled.m Call in +test1 In folder test.m, You can call directly through the following code ：

test1.test()

Of course, as shown in the catalogue ,+test1 There is also a plus sign in the folder +test2 Folder , We want to call... In that folder
test.m, You can do it in the following ways ：

test1.test2.test()

This call format is very similar to the function in the call structure , This is why I call it a directory structure .

Function overloading

Of course, next we will talk about what this part of the catalog is ：

 Current folder ──@cell──dispTest.m
        |
        ├──@double──dispTest.m
        |
        └──untitled.m      

It's like C++ Overloading of functions in , Two @classname Two functions with exactly the same name on the right in the folder of .

Notice what's going on here @ add Class name The format of , It can be MATLAB Own class , It can also be a self-defined class function , Here we set up the folder named by cell class and double precision class .

What's the use of this setting ？ After this setting , For example, I will call dispTest.m Function , If the input variable is a cellular array , Then it will call @cell This function in the folder , If the input variable is double , Then it will call @double Functions in folders .

That is to say, there are two ways to write , Different functions are used ：

dispTest(1)

dispTest({1})

Conclusion

That's about it , about + You can want to be a structure , about @ You can want to overload , The function definitions in my different folders are like this ：

+test1\test.m

function test
disp(' Welcome to your attention slandarer forder1')
end 

+test1+test2\test.m

function test
disp(' Welcome to your attention slandarer forder2')
end 

@cell\dispTest.m

function dispTest(coe)
disp('is cell') 
end  

@double\dispTest.m

function dispTest(coe)
disp('is double') 
end  

So in untitled.m Run the following code , The effect is as follows ：

test1.test()

test1.test2.test()

dispTest(1)

dispTest({
    1})

Welcome to your attention slandarer forder1
Welcome to your attention slandarer forder2
is double
is cell