Question

我想创建一个强制使用字符串作为键的对象接口，但TypeScript编译器会传递代码，即使它有一个数字类型作为键。为什么呢？

例如，

interface PriceI {
    [key:string]:number;
}

var coursePrice: PriceI = {};
coursePrice["Orange"] = 100;
coursePrice["Apple"] = 200;
coursePrice[3]=200;    // It should be compile error, but it pass
coursePrice[true]=300; // It's compile error

Answer 1

请参阅the handbook：

支持的索引签名有两种类型：字符串和数字。可以支持两种类型的索引器，但从数字索引器返回的类型必须是从字符串索引器返回的类型的子类型。这是因为在使用Error: log4j:WARN No appenders could be found for logger (edu.emory.mathcs.nlp.common.util.BinUtils). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. java.io.FileNotFoundException: edu/emory/mathcs/nlp/lexica/en-brown-clusters-simplified-lowercase.xz (No existe el archivo o el directorio) at java.io.FileInputStream.open0(Native Method) at java.io.FileInputStream.open(FileInputStream.java:195) at java.io.FileInputStream.<init>(FileInputStream.java:138) at java.io.FileInputStream.<init>(FileInputStream.java:93) at edu.emory.mathcs.nlp.common.util.IOUtils.createFileInputStream(IOUtils.java:147) at edu.emory.mathcs.nlp.common.util.IOUtils.getInputStream(IOUtils.java:316) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:82) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:72) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:64) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:55) at edu.emory.mathcs.nlp.bin.NLPTrain$1.createGlobalLexica(NLPTrain.java:108) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:193) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:187) at edu.emory.mathcs.nlp.bin.NLPTrain.train(NLPTrain.java:76) at edu.emory.mathcs.nlp.bin.NLPTrain.main(NLPTrain.java:115) java.io.IOException: Stream closed at java.io.BufferedInputStream.getInIfOpen(BufferedInputStream.java:159) at java.io.BufferedInputStream.fill(BufferedInputStream.java:246) at java.io.BufferedInputStream.read1(BufferedInputStream.java:286) at java.io.BufferedInputStream.read(BufferedInputStream.java:345) at java.io.DataInputStream.readFully(DataInputStream.java:195) at java.io.DataInputStream.readFully(DataInputStream.java:169) at org.tukaani.xz.SingleXZInputStream.initialize(Unknown Source) at org.tukaani.xz.SingleXZInputStream.<init>(Unknown Source) at org.tukaani.xz.XZInputStream.<init>(Unknown Source) at org.tukaani.xz.XZInputStream.<init>(Unknown Source) at edu.emory.mathcs.nlp.common.util.IOUtils.createXZBufferedInputStream(IOUtils.java:220) at edu.emory.mathcs.nlp.common.util.IOUtils.createObjectXZBufferedInputStream(IOUtils.java:259) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:82) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:72) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:64) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:55) at edu.emory.mathcs.nlp.bin.NLPTrain$1.createGlobalLexica(NLPTrain.java:108) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:193) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:187) at edu.emory.mathcs.nlp.bin.NLPTrain.train(NLPTrain.java:76) at edu.emory.mathcs.nlp.bin.NLPTrain.main(NLPTrain.java:115) Exception in thread "main" java.lang.NullPointerException at java.io.ObjectInputStream$PeekInputStream.read(ObjectInputStream.java:2338) at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2351) at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2822) at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:804) at java.io.ObjectInputStream.<init>(ObjectInputStream.java:301) at edu.emory.mathcs.nlp.common.util.IOUtils.createObjectXZBufferedInputStream(IOUtils.java:259) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:82) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.getLexiconFieldPair(GlobalLexica.java:72) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:64) at edu.emory.mathcs.nlp.component.template.util.GlobalLexica.<init>(GlobalLexica.java:55) at edu.emory.mathcs.nlp.bin.NLPTrain$1.createGlobalLexica(NLPTrain.java:108) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:193) at edu.emory.mathcs.nlp.component.template.train.OnlineTrainer.train(OnlineTrainer.java:187) at edu.emory.mathcs.nlp.bin.NLPTrain.train(NLPTrain.java:76) at edu.emory.mathcs.nlp.bin.NLPTrain.main(NLPTrain.java:115)进行索引时，JavaScript会在索引到对象之前将其实际转换为number。这意味着使用string（a 100）建立索引与使用number（a "100"）进行索引的情况相同，因此两者需要保持一致。

在您的示例中，TypeScript认为string等同于coursePrice[3] = 200;。

如何在TypeScript接口中强制键类型？

1 个答案: