Objective-C相当于Java函数

Question

我怎样才能编写与此Java代码等效的Objective-C？

public static @Nullable byte[] getUnknownData(Sample s){
    int length = s.data.length-index;
    byte data[] = new byte[length];
    for(int i=0;i<length;i++){
        data[i]=s.data[UNKNOWN_STATUS_INDEX+i].byteValue();
    }
    return data;
}

Objective-C代码：

- (NSData *)getUnknownData:(Sample s) {
    int length = s.data.count-index;
    NSData * data = [NSData alloc]init;
    . . . ????
}

Answer 1

您应该使用NSMutableData，它是NSData的可修改子类：

-(NSData *)getUnknownData:(Sample s){
   int length = s.data.count-index;
   NSMutableData *theData = [NSMutableData dataWithCapacity:length];

   theData.length = length;
   char *theBytes = (char *)theData.mutableBytes;
   for(int i = 0; i < length; ++i) {
       theBytes[i] = (char)[s.data[UNKNOWN_STATUS_INDEX + i] intValue]
   }
   return [theData copy];
}

在保留所需的字节数后，您必须将数组中的每个值转换为数据对象。