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[英]dealloc/deinit called early when using objc_setAssociatedObject in swift
[英]Swift 3.0: “objc_setAssociatedObject” issue
import UIKit
import ObjectiveC
var SubRowObjectKey: String = "subRow"
extension IndexPath {
var subRow: Int {
get {
let subRowObj = objc_getAssociatedObject(self, &SubRowObjectKey)
if subRowObj != nil {
return (subRowObj as! Int)
}
return 0
}
set {
let subRowObj = (newValue as NSInteger)
objc_setAssociatedObject(self, &SubRowObjectKey, subRowObj, .OBJC_ASSOCIATION_RETAIN)
}
}
static func indexPathForSubRow(_ subRow: NSInteger, inRow row: NSInteger, inSection section: NSInteger) -> IndexPath {
var indexPath = IndexPath(row: row, section: section)
indexPath.subRow = (subRow as Int)
print(subRow)
print(indexPath.subRow)
return indexPath
}
}
let indexPath = IndexPath.indexPathForSubRow(5, inRow: 1, inSection: 2)
print(indexPath.subRow)
在Xcode版本8.2.1和Swift 3.0中测试
任何帮助将不胜感激。
IndexPath
是一个结构,它不支持关联的对象。 您可以通过直接尝试回读设置对象来轻松地在setter中检查它:
set {
let subRowObj = (newValue as NSInteger)
objc_setAssociatedObject(self, &SubRowObjectKey, subRowObj, .OBJC_ASSOCIATION_RETAIN)
let subRowObj2 = objc_getAssociatedObject(self, &SubRowObjectKey)
print(subRowObj2 ?? "nil") // prints "nil"
}
即使setter中的代码有效 ,整个构造仍然不成立:由于结构在传输/分配时被复制(至少通过写入机制上的复制进行修改),因此相关对象将不包含在复制,所以你迟早会丢失这些信息。
然而,不是扩展IndexPath
你可以扩展NSIndexPath
然后工作正常 - 但我想这不是你想要的,因为你想影响从表视图得到的IndexPath ...
根据maddy的回答,这是我的IndexPath扩展,它添加了一个subRow属性。
extension IndexPath {
init(subRow: Int, row: Int, section: Int) {
self.init(indexes: [IndexPath.Element(section), IndexPath.Element(row), IndexPath.Element(subRow)])
}
var subRow: Int {
get { return self[index(at: 2)] }
set { self[index(at: 2)] = newValue }
}
var row: Int {
get { return self[index(at: 1)] }
set { self[index(at: 1)] = newValue }
}
var section: Int {
get { return self[index(at: 0)] }
set { self[index(at: 0)] = newValue }
}
private func index(at idx: Int) -> IndexPath.Index {
return self.startIndex.advanced(by: idx)
}
}
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