有如下类
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| open class BaseEntity {
var createDt: Date = Date()
var updateDt: Date = Date()
var deleted: Boolean = false
var version: Long = 0
}
data class Device(
val imei: String,
val sn: String,
val productName: String,
val productType: String
) : BaseEntity()
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1. 数据类调用copy后, 会导致BaseEntity类中的字段丢失, 测试用例如下:
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| @Test
fun testDataClassCopy() {
val device = JSON.parse<Device>("""{ "imei": "358730091744037", "sn": "G6TXXNZPKPJ3", "productName": "iPhone OS", "productType": "iPhone11,6", "createDt":"2019-08-18 19:35:00","updateDt":"2019-08-18 19:35:00","deleted":false,"version":3 }""")
assertEquals(device.version, 3)
val newDevice = device.copy(imei = "this is imei")
assertEquals(newDevice.version, 0)
}
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以上测试用例通过. 为什么呢? version字段明明是3, 怎么变成了0呢? 我们看看Device类中copy方法反编译后的java代码
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| @NotNull
public final Device copy(@NotNull String imei, @NotNull String sn, @NotNull String productName, @NotNull String productType) {
Intrinsics.checkParameterIsNotNull(imei, "imei");
Intrinsics.checkParameterIsNotNull(sn, "sn");
Intrinsics.checkParameterIsNotNull(productName, "productName");
Intrinsics.checkParameterIsNotNull(productType, "productType");
return new Device(imei, sn, productName, productType);
}
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从代码可以看出, Device的父类BaseEntity中的字段并没有在copy方法中出现. 导致父类中的字段全部变成了默认值.