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makeIncrementer

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ios - 努力理解为什么 "Capturing by reference ensures that runningTotal and amount do not disappear when the call to makeIncrementer ends' ?

我是Swift的新手,正在尝试学习捕获值的概念。我从“TheSwiftProgrammingLanguage2.1”看到这个:funcmakeIncrementer(forIncrementamount:Int)->()->Int{varrunningTotal=0funcincrementer()->Int{runningTotal+=amountreturnrunningTotal}returnincrementer}letincrementByTen=makeIncrement(forIncrement:10)incrementByTen()“Theincrementer()fu