Phenomenon 现象

// 某个Date类型的日期
let date: Date = ...
// 生成BLE设备需要的`UInt32`类型的时间戳
let toPeripheralTimestamp: UInt32 = UInt32(date)

线上出现如下两类CRASH:

1. Inline: Swift runtime failure: Double value cannot be converted to UInt32 because the result would be greater than UInt32.max
2. Double value cannot be converted to UInt32 because it is either infinite or NaN

Analysis 分析

1. 发生CRASH的确切位置是 UInt32(date), 更近一步说是如下初始化方法:

/// Creates an integer from the given floating-point value, rounding toward zero.
/// 译: 从给定的浮点值创建一个整数，向零舍入。
/// Any fractional part of the value passed as `source` is removed, rounding the value toward zero. eg: let x = Int(21.7), x = 21
/// 译: 作为 source 传递的值的任何小数部分都将被删除，将值向零取整。eg: let x = Int(21.7), x = 21
public init(_ source: Double)

2. 为什么会CRASH ? 官方解释如下:

If source is outside the bounds of this type after rounding toward zero, a runtime error may occur.
译: 如果 source 在向零舍入后超出此类型的范围，则可能会发生运行时错误。

3. 当 source 为 Double 类型时, 有如下几种超出类型范围的 CRASH 可能:

// 会提示: Double value cannot be converted to UInt32 because it is either infinite or NaN
a. Double.infinite, Double.nan
// Error: ...the result would be less than UInt.min
b. 负数
// Error: ...result would be greater than UInt32.max
c. 大于 UInt32.max 的浮点数

Solution 解决方法

//
//  MIWSafe.swift
//  xxxxxxx
//
//  Created by 侯仕奇 on 2023/3/8.
//  Copyright © 2023 零下引力. All rights reserved.
//import Foundationclass SQISafe {public static func sqiUInt32(_ source: Double) -> UInt32 {guard !source.isNaN else {return UInt32.zero}guard !source.isInfinite else {return UInt32.max}guard source < Double(UInt32.max) else {return UInt32.max}return UInt32(source)}
}

Instruction 怎样使用 ?

// 某个Date类型的日期
let date: Date = ...
// 生成BLE设备需要的`UInt32`类型的时间戳
let toPeripheralTimestamp: UInt32 = SQISafe.sqiUInt32(date)

Others

/// Positive infinity. 正无穷大。
Double.infinity
/// A quiet NaN ("not a number").
Double.nan