What are the selection and design specifications for function return types?

Function return type design principles: semantics, predictability, consistency, compatibility and scalability. Recommended specifications: basic types, custom types, null values, multiple values, error handling.

Selection and design specifications of function return type

The function return type is an important part of function design, which determines the function The result of the call. Choosing the right return type can improve the readability, maintainability, and safety of your code.

Principles for selecting return types

• Semanticization: The return type should clearly express the type and semantics of the value returned by the function.
• Predictability: Functions should return the same type of return value in all cases.
• Consistency: Similar functions should have similar return types.
• Compatibility: The return type should be compatible with the function's input parameter types.
• Extensibility: The return type should allow the function to be easily extended in the future.

Design specifications

The following are recommended specifications for how to design function return types:

• Basic types:For functions that return simple values, use basic types (such as int, float, bool).
• Custom types: For functions that return complex objects, use custom types.
• Null value: For objects that may return null or empty values, use nullable types (such as Nullable).
• Multiple values: For functions that need to return multiple values, use tuples, arrays, or sets.
• Error handling: For functions that may fail, throw an exception or use a return code.

Practical case

The following is a function that calculates the sum of two numbers. The function returns an integer result:

public int Add(int a, int b)
{
    return a + b;
}

In In this example, the return type int clearly indicates that the function returns the sum of two numbers consistent with the input parameter types.

Error Codes

For functions that may fail, you can throw an exception or use a return code. The following functions use an error code to indicate a calculation failure:

public int Divide(int a, int b)
{
    if (b == 0)
    {
        return -1; // Error code for division by zero
    }
    return a / b;
}

null value

For objects that may return null or empty values, you can use nullable types. The following function uses the nullable type int? to return the result of a calculation and returns null if the divisor is zero:

public int? Divide(int a, int b)
{
    if (b == 0)
    {
        return null; // Null indicates division by zero
    }
    return a / b;
}

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