术语“声明”和“定义”在 Apple 的 Swift 文档中被用作同义词，这让我感到困惑。
在“初始化”部分(讨论类初始化器)下，Apple 声明:
You can set an initial value for a stored property within an initializer, or by assigning a default property value as part of the property’s definition.
他们在小节中进一步说明:
You can set the initial value of a stored property from within an initializer, as shown above. Alternatively, specify a default property value as part of the property’s declaration.
我认为变量声明不同于变量定义。
最佳答案
你是对的，这两个意思不同，虽然我认为大多数人只是以相同的意思使用它们，我认为那些 AppleDocs 也是如此。 Here is great article关于主题:
总结
A declaration provides basic attributes of a symbol: its type and its name. A definition provides all of the details of that symbol--if it's a function, what it does; if it's a class, what fields and methods it has; if it's a variable, where that variable is stored. Often, the compiler only needs to have a declaration for something in order to compile a file into an object file, expecting that the linker can find the definition from another file. If no source file ever defines a symbol, but it is declared, you will get errors at link time complaining about undefined symbols.
关于ios - Swift 中变量声明和定义的区别，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31580432/