ios - 无法在 JSON 解析中将 NSNumber 桥接到 Float

Question

得到这个错误:

Fatal error: Unable to bridge NSNumber to Float. What is the problem?

这是原始消息，它是 float 而不是字符串。

{\"name\":\"Tomas\",\"gender\":\"male\",\"probability\":0.99,\"count\":594}

Answer 1

在 Swift/Foundation 中有许多不同类型的数字。您的 NSKeyValueCoding 已设置为 NSNumber 的实例(请参阅下面的 JSON 序列化文档摘录)，因此您需要按原样阅读，然后要求转换此 NSNumber 作为 Float 如果需要的话:

if let n = d.value(forKey: "probability") as? NSNumber {
    let f = n.floatValue
}

JSONSerialization 文档说:

A Foundation object that may be converted to JSON must have the following properties:

• The top level object is an NSArray or NSDictionary.
• All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
• All dictionary keys are instances of NSString.
• Numbers are not NaN or infinity.