帮我看看这段代码报错：nil dereference in map update
for channel, productBasicInfos := range channelProductBasicInfos {
for _, productBasicInfo := range productBasicInfos {
calendar := productSymbolCalendarMap[productBasicInfo.Symbol]
channelProductExpectSettlementDayMap[channel] = append(channelProductExpectSettlementDayMap[channel], ChannelProductExpectSettleDay{
Channel: channel, Symbol: productBasicInfo.Symbol,
SubExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_BUY)).ToDateStruct().ToStdTime(),
RedExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_SELL)).ToDateStruct().ToStdTime(),
})

    }
}

你的代码中 nil dereference in map update 错误很可能是由于 calendar 变量为 nil。这是因为 productSymbolCalendarMap[productBasicInfo.Symbol] 返回 nil 时，代码尝试调用 calendar.NextSettlementDay 方法，从而导致 nil dereference 错误。

为了避免这个错误，你需要在调用 calendar.NextSettlementDay 之前检查 calendar 是否为 nil。修改后的代码如下：

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for channel, productBasicInfos := range channelProductBasicInfos {
	for _, productBasicInfo := range productBasicInfos {
		calendar, ok := productSymbolCalendarMap[productBasicInfo.Symbol]
		if !ok || calendar == nil {
			// 处理 calendar 为空的情况，可以记录错误日志或跳过这个 productBasicInfo
			continue
		}
		channelProductExpectSettlementDayMap[channel] = append(channelProductExpectSettlementDayMap[channel], ChannelProductExpectSettleDay{
			Channel: channel, Symbol: productBasicInfo.Symbol,
			SubExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_BUY)).ToDateStruct().ToStdTime(),
			RedExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_SELL)).ToDateStruct().ToStdTime(),
		})
	}
}

这样，在调用 calendar.NextSettlementDay 方法之前，先检查 calendar 是否为 nil，从而避免了 nil dereference 错误。

——来自AI问答宝 https://ai.wendabao.net

还是报错这个：nil dereference in map update
// 计算所有产品的预估结算日
startDate = carbon.Now().ToDateStruct()
var channelProductExpectSettlementDayMap ChannelProductExpectSettleDayMap

for channel, productBasicInfos := range channelProductBasicInfos {
    for _, productBasicInfo := range productBasicInfos {
        calendar,ok := productSymbolCalendarMap[productBasicInfo.Symbol]
        if !ok || calendar == nil {
            // 处理 calendar 为空的情况，可以记录错误日志或跳过这个 productBasicInfo
            continue
        }
        // key -> value  ===> channel -> ChannelProductExpectSettleDay
        channelProductExpectSettlementDayMap[channel] = append(channelProductExpectSettlementDayMap[channel], ChannelProductExpectSettleDay{
            Channel: channel, Symbol: productBasicInfo.Symbol,
            SubExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_BUY)).ToDateStruct().ToStdTime(),
            RedExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_SELL)).ToDateStruct().ToStdTime(),
        })

    }
}

你的代码依旧出现 nil dereference 错误，可能是因为 channelProductExpectSettlementDayMap 没有正确初始化。你需要确保 channelProductExpectSettlementDayMap 在使用之前已被正确初始化。

可以尝试以下修改：

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// 计算所有产品的预估结算日
startDate := carbon.Now().ToDateStruct()
channelProductExpectSettlementDayMap := make(ChannelProductExpectSettleDayMap)

for channel, productBasicInfos := range channelProductBasicInfos {
	for _, productBasicInfo := range productBasicInfos {
		calendar, ok := productSymbolCalendarMap[productBasicInfo.Symbol]
		if !ok || calendar == nil {
			// 处理 calendar 为空的情况，可以记录错误日志或跳过这个 productBasicInfo
			continue
		}
		// 初始化 map 中的 slice，如果它还没有被初始化
		if channelProductExpectSettlementDayMap[channel] == nil {
			channelProductExpectSettlementDayMap[channel] = []ChannelProductExpectSettleDay{}
		}
		// key -> value  ===> channel -> ChannelProductExpectSettleDay
		channelProductExpectSettlementDayMap[channel] = append(channelProductExpectSettlementDayMap[channel], ChannelProductExpectSettleDay{
			Channel: channel, Symbol: productBasicInfo.Symbol,
			SubExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_BUY)).ToDateStruct().ToStdTime(),
			RedExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_SELL)).ToDateStruct().ToStdTime(),
		})
	}
}

在这段代码中，我们添加了对 channelProductExpectSettlementDayMap[channel] 的 nil 检查并初始化，确保在尝试对其进行 append 操作之前，它已经是一个有效的 slice。这样可以避免 nil dereference 错误。

——来自AI问答宝 https://ai.wendabao.net

这两句有什么区别？

这两句代码的确有不同之处，具体如下：

  1. var channelProductBasicInfos map[string]mktmapping.ProductBasicInfos

    这一句声明了一个名为 channelProductBasicInfos 的变量，类型是 map[string]mktmapping.ProductBasicInfos，但是没有对它进行初始化。因此，这个变量在声明时的初始值是 nil，如果直接对它进行读写操作，会导致 nil dereference 错误。

  2. channelProductBasicInfos := make(ChannelProductExpectSettleDayMap)

    这一句则是初始化了一个名为 channelProductBasicInfos 的变量，并且调用 make 函数将其初始化为一个空的 ChannelProductExpectSettleDayMap。这样，channelProductBasicInfos 就可以被安全地使用了。

区别总结

  • var 声明只声明变量，不初始化，默认值是 nil。
  • make 初始化变量，并分配内存，避免 nil dereference 错误。

在你的代码中的应用

结合你之前的代码，可以确保 channelProductExpectSettlementDayMap 被正确初始化以避免 nil dereference 错误：

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// 计算所有产品的预估结算日
startDate := carbon.Now().ToDateStruct()
channelProductExpectSettlementDayMap := make(ChannelProductExpectSettleDayMap) // 初始化 map

for channel, productBasicInfos := range channelProductBasicInfos {
	for _, productBasicInfo := range productBasicInfos {
		calendar, ok := productSymbolCalendarMap[productBasicInfo.Symbol]
		if !ok || calendar == nil {
			// 处理 calendar 为空的情况，可以记录错误日志或跳过这个 productBasicInfo
			continue
		}
		// 初始化 map 中的 slice，如果它还没有被初始化
		if channelProductExpectSettlementDayMap[channel] == nil {
			channelProductExpectSettlementDayMap[channel] = []ChannelProductExpectSettleDay{}
		}
		// key -> value  ===> channel -> ChannelProductExpectSettleDay
		channelProductExpectSettlementDayMap[channel] = append(channelProductExpectSettlementDayMap[channel], ChannelProductExpectSettleDay{
			Channel: channel, Symbol: productBasicInfo.Symbol,
			SubExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_BUY)).ToDateStruct().ToStdTime(),
			RedExpectSettleDate: calendar.NextSettlementDay(startDate, productBasicInfo.GetSettlementDayByDirection(orderconstant.W_TRX_DIR_SELL)).ToDateStruct().ToStdTime(),
		})
	}
}

通过上述代码的初始化，确保 channelProductExpectSettlementDayMap 和其中的 slice 被正确初始化，从而避免 nil dereference 错误。

——来自AI问答宝 https://ai.wendabao.net

License

本文采用 署名-非商业性使用-相同方式共享 4.0 国际 许可协议，转载请注明出处。