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Howto:Coding a simple Nasal Framework: Difference between revisions
Howto:Coding a simple Nasal Framework (view source)
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(Created page with "{{WIP}} == Objective == Illustrate the basic thought process required to come up with Nasal/Canvas code that is sufficiently generic to support the following requirements * s...") |
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We'll be using the PFD/ND code as an example here, and won't be using any complicated techniques. | We'll be using the PFD/ND code as an example here, and won't be using any complicated techniques. | ||
== Variables == | |||
In order to support independent instances of each instrument, you need to use separate variables, so rather than having something like this at global scope: | |||
<syntaxhighlight lang="nasal"> | |||
var horizon = nil; | |||
var markerBeacon = nil; | |||
var markerBeaconText = nil; | |||
var speedText = nil; | |||
var machText = nil; | |||
var altText = nil; | |||
var selHdgText = nil; | |||
var fdX = nil; | |||
var fdY = nil; | |||
</syntaxhighlight> | |||
You would instead use a hash, and populate it with your variables: | |||
<syntaxhighlight lang="nasal"> | |||
var PrimaryFlightDisplay= { | |||
new: func() { return {parents:[PrimaryFlightDisplay],}; }, | |||
# set up fields | |||
horizon: nil, | |||
markerBeacon: nil, | |||
markerBeaconText: nil, | |||
speedText: nil, | |||
machText: nil, | |||
altText: nil, | |||
selHdgText: nil, | |||
fdX: nil, | |||
fdY:nil, | |||
}; | |||
</syntaxhighlight> | |||
The same thing can be accomplished by doing something like this in your constructor, using a temporary object: | |||
<syntaxhighlight lang="nasal"> | |||
var PrimaryFlightDisplay= { | |||
new: func() { | |||
var m = {parents:[PrimaryFlightDisplay]}; | |||
m.horizon = nil; | |||
m.markerBeacon = nil; | |||
m.markerBeaconText = nil; | |||
m.speedText = nil; | |||
m.machText = nil; | |||
m.altText = "Hello World"; | |||
m.selHdgText = nil; | |||
m.fdX = nil; | |||
m.fdY = nil; | |||
return m; | |||
}, | |||
}; | |||
</syntaxhighlight> | |||
To create a new object, you would then simply have to call the .new() function: | |||
<syntaxhighlight lang="nasal"> | |||
var myPFD = PrimaryFlightDisplay.new(); | |||
print( myPDF.altText ); | |||
</syntaxhighlight> | |||
By using this method, you can easily create dozens of independent instances of your class: | |||
<syntaxhighlight lang="nasal"> | |||
var PFDVector = []; | |||
forindex(var i=0;i<100;i+=1) | |||
append(PFDVector, PrimaryFlightDisplay.new() ); | |||
</syntaxhighlight> | |||
== Dealing with Properties == | |||