找不到成员下标 [英] could not find member subscript

问题描述

我正在尝试执行以下代码并收到错误 Could not find member 'subscript on Xcode6

I am trying to execute the following code and getting the error Could not find member 'subscript on Xcode6

var b:[[Float]] = [[1,2]]

var i2 = 0 // second to last control point
var pointIm1 = CGPoint(x: 0.0,y: 0.0)
var pointI = CGPoint(x: 0.0,y: 0.0)
var pointIp1 = CGPoint(x: 0.0,y: 0.0)
var px:Float = b[0][0] * Float(pointIm1.x) + b[0][0] * Float(pointI.x) + b[0][0] + b[0][0] * Float(pointIp1.x)

任何人都知道为什么会出错

Anyone has idea why is giving error

有没有人有更好的主意，或者我需要像 Nate 在他的回答中建议的那样为每个下标创建不同的变量

Do anyone have better idea or i need to create different variables for each subscript as Nate suggested in his answer

//not looks good
var bj0 = b[j][0]
var bj1 = b[j][1]
var bj2 = b[j][2]
var bj3 = b[j][3]


var px:Float = bj0 * Float(pointIm1.x) + bj1 * Float(pointI.x) + bj2 + bj3 * Float(pointIp1.x)

推荐答案

下标不是问题 - Swift 在尝试解析较长的多项目表达式(如最后一行)时遇到了麻烦.在操场上，我收到此错误:

It isn't a problem with the subscript - Swift gets into trouble when trying to parse longer multi-item expressions like your final line. In a playground I get this error:

表达式太复杂，无法在合理的时间内解决；考虑将表达式分解为不同的子表达式

expression was too complex to be solved in reasonable time; consider breaking up the expression into distinct sub-expressions

您需要重构该行以克服此限制 - 类似于:

You'll need to refactor that line to get past this limitation - something like:

let b00 = b[0][0]
var px: Float = b00 * Float(pointIm1.x) + b00 * Float(pointI.x) + b00 + b00 * Float(pointIp1.x)

<小时>

你可以把它分成两步，像这样:

---

You could probably just break it up into two steps, like this:

var px:Float = bj0 * Float(pointIm1.x) + bj1 * Float(pointI.x)
px += bj2 + bj3 * Float(pointIp1.x)

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