子类 NSTextStorage 会导致严重的内存问题

Question

我有一个自定义的UITextView，它通过定义一个自定义的NSTextStorage 类来利用 Apple 的 TextKit，但是，当我将我的子类用于自定义文本视图的文本存储（如下所示）并尝试打开任何文件时大于 20.0KB，应用程序由于内存泄漏而崩溃：“Message from debugger: Terminated due to memory issue”。

奇怪的是，如果我用标准的NSTextStorage 替换我的自定义BMTextStorage，文本会立即加载而没有任何内存泄漏，并且使用

TextView.swift

class TextView : UITextView {

    required init(frame: CGRect) {

        // If I replace the following line with simply 
        // "let textStorage = NSTextStorage()"
        // I can open any file of any size and not have a memory leak
        // issue, using only about 20-30MB of RAM. If I ran this code
        // as is, it can open most files less than 20KB but will 
        // crash otherwise.
        let textStorage = BMTextStorage() 

        let layoutManager = NSLayoutManager()

        layoutManager.allowsNonContiguousLayout = true

        let textContainer = NSTextContainer(size: CGSizeMake(.max, .max))

        textContainer.widthTracksTextView = true
        textContainer.heightTracksTextView = true
        textContainer.exclusionPaths = [UIBezierPath(rect: CGRectMake(0.0, 0.0, 40.0, .max))]

        layoutManager.addTextContainer(textContainer)
        textStorage.addLayoutManager(layoutManager)

        super.init(frame: frame, textContainer: textContainer)

        textStorage.delegate = self
        layoutManager.delegate = self

    }

}

BMTextStorage.swift

typealias PropertyList = [String : AnyObject]

class BMTextStorage : NSTextStorage {

    override var string: String {
        return storage.string
    }

    private var storage = NSMutableAttributedString()

    override func attributesAtIndex(location: Int, effectiveRange range: NSRangePointer) -> PropertyList {
        return storage.attributesAtIndex(location, effectiveRange: range)
    }

    override func replaceCharactersInRange(range: NSRange, withString str: String) {
        storage.replaceCharactersInRange(range, withString: str)
        edited([.EditedAttributes, .EditedCharacters], range: range, changeInLength: str.length - range.length)
    }

    override func setAttributes(attrs: PropertyList?, range: NSRange) {
        storage.setAttributes(attrs, range: range)
        edited([.EditedAttributes], range: range, changeInLength: 0)
    }

    override func processEditing() {
        super.processEditing()
    }

 }

Answer 1

哇....很奇怪，当我将storage 的类型更改为NSTextStorage...时，它得到了修复。

typealias PropertyList = [String : AnyObject]

class BMTextStorage : NSTextStorage {

    overrride var string: String {
        return storage.string
    }

    private var storage = NSTextStorage()

    override func attributesAtIndex(location: Int, effectiveRange range: NSRangePointer) -> PropertyList {
        return storage.attributesAtIndex(location, effectiveRange: range)
    }

    override func replaceCharactersInRange(range: NSRange, withString str: String) {
        storage.replaceCharactersInRange(range, withString: str)
        edited([.EditedAttributes, .EditedCharacters], range: range, changeInLength: str.length - range.length)
    }

    override func setAttributes(attrs: PropertyList?, range: NSRange) {
        storage.setAttributes(attrs, range: range)
        edited([.EditedAttributes], range: range, changeInLength: 0)
    }

    override func processEditing() {
        super.processEditing()
    }

 }