SWIFT：编译时出现警告，但表现良好

Question

我的代码运行正常，除了在编译时发出警告这一事实，我真的不知道这些是从哪里来的，因为我正在自学。我如何修改我的代码（FIXME BEGIN 和 FIXME END 之间的部分）以使代码在没有警告的情况下编译？

代码：

protocol EqualsMethod {
    // Notice that the type-keyword  "Self" helps to solve the
    // curriously recurring interface pattern for direct self-reference
    // FIXME-begin
    func equality(my: Self) -> Bool;
    // FIXME-end
}

struct my_int : EqualsMethod {
    // FIXME-begin
    func equality(my: my_int) -> Bool{
        if (my.value == value){
            return true;
        }
        return false
    }
    // FIXME-end

    var value: Int;
}

// Returns the index of an element if it exists
// nil otherwise
func findIndex
    // FIXME-begin
    <T: EqualsMethod>
    // FIXME-end
    (valueToFind: T, array:[T]) -> Int? {

        // FIXME-begin
        for (k, e) in array.enumerated(){
            if (valueToFind.equality(my: e))
            {
                return k;
            }
        }
        // FIXME-end

        // Index not found
        return nil
}

let ints = [my_int(value: 1),
            my_int(value: 2),
            my_int(value: 3),
            my_int(value: 4),
            my_int(value: 5)]

print(findIndex(valueToFind: my_int(value: 2), array: ints))
print(findIndex(valueToFind: my_int(value: 0), array: ints))

预期输出：

Optional(1)
nil

警告：

main.swift:49:7: warning: expression implicitly coerced from 'Int?' to 'Any'                                            
print(findIndex(valueToFind: my_int(value: 2), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
main.swift:49:7: note: provide a default value to avoid this warning                                                    
print(findIndex(valueToFind: my_int(value: 2), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                            ?? <#default value#>                                        
main.swift:49:7: note: force-unwrap the value to avoid this warning                                                     
print(findIndex(valueToFind: my_int(value: 2), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                           !                                                            
main.swift:49:7: note: explicitly cast to 'Any' with 'as Any' to silence this warning                                   
print(findIndex(valueToFind: my_int(value: 2), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                            as Any                                                      
main.swift:50:7: warning: expression implicitly coerced from 'Int?' to 'Any'                                            
print(findIndex(valueToFind: my_int(value: 0), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
main.swift:50:7: note: provide a default value to avoid this warning                                                    
print(findIndex(valueToFind: my_int(value: 0), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                            ?? <#default value#>                                        
main.swift:50:7: note: force-unwrap the value to avoid this warning                                                     
print(findIndex(valueToFind: my_int(value: 0), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                           !                                                            
main.swift:50:7: note: explicitly cast to 'Any' with 'as Any' to silence this warning                                   
print(findIndex(valueToFind: my_int(value: 0), array: ints))                                                            
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                                                             
                                                            as Any

Answer 1

findIndex()returnsInt?，然后print()将其强制为Any.

自警告以来，应用建议的修复之一：

print(findIndex(valueToFind: my_int(value: 2), array: ints) ?? -1) // one option
print(findIndex(valueToFind: my_int(value: 2), array: ints)!) // another option, may crash
print(findIndex(valueToFind: my_int(value: 2), array: ints) as Any) // third option

SWIFT：编译时出现警告，但表现良好

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