在下面的代码中,第一个日志语句按预期显示小数,但第二个日志为NULL。我究竟做错了什么?

NSDictionary *entry = [[NSDictionary alloc] initWithObjectsAndKeys:
  @"x", [NSNumber numberWithDouble:acceleration.x],
  @"y", [NSNumber numberWithDouble:acceleration.y],
  @"z", [NSNumber numberWithDouble:acceleration.z],
  @"date", [NSDate date],
  nil];
NSLog([NSString stringWithFormat:@"%@", [NSNumber numberWithDouble:acceleration.x]]);
NSLog([NSString stringWithFormat:@"%@", [entry objectForKey:@"x"]]);

最佳答案

您正在交换插入对象和键的顺序:您需要先插入对象,然后再插入键,如以下示例所示。

NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];

关于iphone - 创建一个NSDictionary,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/1107996/

10-12 00:18
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