Swift 4.0中'>>>-'运算符是什么？为何Xcode报未解析错误？

Hey there! Let's unpack what's going on with this mysterious >>>- operator you've run into.

First: This isn't a standard Swift operator #

Swift 4.0 (and all subsequent versions of Swift) does not include >>>- as part of its standard library. That's why Xcode is throwing the "Use of unresolved operator '>>>-'" error — the compiler has no idea what this operator is supposed to do because it's not built into the language.

So why did you see it in source code? #

Chances are, >>>- is a custom operator defined somewhere in the codebase you're looking at. Swift gives developers full control to create their own operators for specific use cases — here are some common scenarios where custom operators pop up:

• Functional programming patterns (like chaining operations or handling monadic types)
• Domain-specific logic (simplifying repeated, project-specific tasks)
• Wrappers for asynchronous operations or state management

To confirm this, try searching the entire codebase for the operator's definition. You'll likely find something like this somewhere:

// Example of a custom infix operator definition
infix operator >>>-: AssignmentPrecedence

// The actual implementation of what the operator does
func >>>-<T, U>(lhs: T, rhs: (T) -> U) -> U {
    // Custom logic here, e.g., transforming lhs with rhs function
    return rhs(lhs)
}

Why the error happens? #

The error pops up because:

1. The file where you're using >>>- hasn't imported the module or source file that defines the operator, OR
2. The code that defines >>>- isn't included in your project's build target (so the compiler never sees it)

How to fix it? #

• Locate the operator's definition in the source code (search for operator >>>-)
• Make sure the file containing the definition is added to your project's build phases
• If it's part of a separate module, add an import [ModuleName] statement at the top of the file where you're using the operator

内容的提问来源于stack exchange，提问作者Wimal Weerawansa