NSString drawInRect设置上下文 [英] NSString drawInRect set context

问题描述

我在背景上绘制了一些图像。有时我的应用程序因奇怪的错误而崩溃：

I draw some image in background. Sometimes my app crashes with strange error:

功能签名专门化< Arg [0] =属于MyApp。

function signature specialization < Arg[0] = Owned To Guaranteed> of MyApp.

我检查了所有崩溃，并通过不使用上下文的方法获得了所有崩溃。其中之一绘制文本。

I checked all crashes, and I get all of them on methods that do not use context. One of them draw text. How can I specify context to draw text?

UIGraphicsBeginImageContextWithOptions(size, false, 1.0)
let ctx = UIGraphicsGetCurrentContext()
// some code
str.drawInRect(CGRectMake(floor(10 * scaleFactor), yOffset, size.width, floor(60 * scaleFactor)), withAttributes: textFontAttributes)
// code
let img = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

编辑

我没有找到在特定上下文中绘制文本的任何方法。我在绘制文本之前使用 UIGraphicsPushContext（ctx），在绘制文本后使用 UIGraphicsPopContext（）。 https://stackoverflow.com/a/10402637/820795

Edit

I do not found any method to draw text in specific context. I use UIGraphicsPushContext(ctx) before draw text and UIGraphicsPopContext() after. https://stackoverflow.com/a/10402637/820795

推荐答案

我不认为这与绘图有关。当Swift API中有一个错误时， Objective-C需要将nil参数值传递给Swift，但此参数的Swift版本未键入Optional，就会出现函数签名专门化。

I'm not convinced that this has anything to do with drawing. The "function signature specialization" arises when there's a mistake in the Swift APIs where Objective-C needs to pass a nil parameter value to Swift, but the Swift version of this parameter is not typed as an Optional.

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