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that each of them have different purposes. These are; hObject, eventdata and handles. If
each of them is not used in the ‘callback’ function the guide will put an underline warning
sign on each of them.
hObject: This variable handles the event of current operating object or component which
creates a ‘getcallbackobject’ called GCBO. In MATLAB, the GCBO are dynamically created
each time when a callback is executed. Their functionality is to get handle to current
callback object [OBJECT, FIGURE] = GCBO and returns the handle of the object whose
callback is currently executing and also the figure containing that object. [36]
eventdata: The event data in MATLAB take event handlings data and pass throughout the
platform. These are reserved for future version of MATLAB.
handles: This method is the basic for MATLAB GUI events. When MATLAB creates a
graphics object or component, it assigns an identifier to the object. [37] This identifier is
called ‘handle’ and sometimes denoted as ‘h’. One can use the “handle” identifier variable
to access the “hObject” properties with two built in functions called “set” and “get”
functions. For example, the following quadratic statements create a graph and return an
event data to a plot result object in a form of h:
𝑥 = 0: 0.1: 1
𝑦 = 2𝑥 2 + 𝑥
ℎ = 𝑝𝑙𝑜𝑡(𝑥, 𝑦)
We can use the handle event handler h to set and get the properties of the ‘quadratic
plot’ object. For example, we can set its fore ground colour property as:
Set (h,'Color','red')
We can also specify the properties when we call the plotting function in another M-script
file:
h = plot(x, y,'Color','red');
We can also get the object property by using a get function. And it will return the object
and its possible values as numerical value which is an id for that component and its
property.
A= get (gcf,’Color’), where gcf returns the current figure,
and it stands for get current figure.
Will return
ans=
0.2 0.2 0.1
This value is the combination of one of the MATLAB colour RGB.
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