Fix memory leak after rendering

[YusukeOba]

Issue Link 🔗

#3671
#3649

Goals ⚽

No memory leak.

Implementation Details 🚧

• Added weak modifier to NSUIAccessibilityElement#container.
• Added guard statements.

Testing Details 🔍

I tested in example demo and my project.

[codecov-io]

Codecov Report

Merging #3680 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3680      +/-   ##
==========================================
- Coverage   31.06%   31.01%   -0.06%     
==========================================
  Files         114      114              
  Lines       10465    10482      +17     
==========================================
  Hits         3251     3251              
- Misses       7214     7231      +17

Impacted Files	Coverage Δ
Source/Charts/Utils/Platform+Accessibility.swift	31.57% <ø> (ø)	⬆️
Source/Charts/Renderers/LegendRenderer.swift	53.06% <0%> (-0.92%)	⬇️
Source/Charts/Renderers/BarChartRenderer.swift	50.68% <0%> (-0.79%)	⬇️
...ce/Charts/Renderers/CandleStickChartRenderer.swift	0% <0%> (ø)	⬆️

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[YusukeOba]

@liuxuan30
@petester42

Would you be able to review this source code?

I think there is a problem of cyclic reference by #1060.

Example in LineChartRenderer.

1. Create and hold NSUIAccessibilityElement. depends on ChartView.
   https://github.com/danielgindi/Charts/blob/master/Source/Charts/Renderers/LineChartRenderer.swift#L621

2. NSUIAccessibilityElement strong reference on ChartView.
   https://github.com/danielgindi/Charts/blob/98a472cf77a419e63a5a853b04515cb3d4f34079/Source/Charts/Utils/Platform%2BAccessibility.swift#L107

[pmairoldi]

I’ll look at it sometime this weak

[pmairoldi]

Good catch. Looks good but this change needs to be applied to both macOS and iOS/tvOS variations. Just search for class NSUIAccessibilityElement you should find it easily.

[YusukeOba]

Sorry about that. I fixed for macOS. 😃

[pmairoldi]

Thanks

[YusukeOba]

Thank you for your time. 😄