ios 为什么我在objective-c中得到一个整数到指针转换错误？
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Why am I getting an integer to pointer conversion error in objective-c?
提问by Justin Copeland
I am looping through an NSString object called previouslyDefinedNSStringand verifying if the integer representing the ASCII value of a letter is in an NSMutableSet called mySetOfLettersASCIIValues, which I had previously populated with NSIntegers:
我正在循环调用 NSString 对象previouslyDefinedNSString并验证表示字母 ASCII 值的整数是否在名为 的 NSMutableSet 中mySetOfLettersASCIIValues，我之前用 NSIntegers 填充了该对象：
NSInteger ASCIIValueOfLetter;
for (int i; i < [previouslyDefinedNSString length]; i++) {
ASCIIValueOfLetter = [previouslyDefinedNSString characterAtIndex:i];
// if character ASCII value is in set, perform some more actions...
if ([mySetOfLettersASCIIValues member: ASCIIValueOfLetter])
However, I am getting this error within the condition of the IF statement.
但是，我在 IF 语句的条件下收到此错误。
Incompatible integer to pointer conversion sending 'NSInteger' (aka 'int') to parameter of type 'id';
Implicit conversion of 'NSInteger' (aka 'int') to 'id' is disallowed with ARC
What do these errors mean? How am I converting to an object type (which id represents, right?)? Isn't NSInteger an object?
这些错误是什么意思？我如何转换为对象类型（哪个 id 代表，对吧？）？NSInteger 不是一个对象吗？
回答by Maurício Linhares
You want to make it an NSNumber, as in:
你想让它成为一个 NSNumber，如：
NSInteger ASCIIValueOfLetter;
for (int i; i < [previouslyDefinedNSString length]; i++) {
ASCIIValueOfLetter = [previouslyDefinedNSString characterAtIndex:i];
// if character ASCII value is in set, perform some more actions...
if ([mySetOfLettersASCIIValues member: [NSNumber numberWithInteger: ASCIIValueOfLetter]])
Now you're going to have the result you're looking for.
现在，您将获得想要的结果。
回答by Itai Ferber
These errors mean that member:expects an object. idis a pointer to an Objective-C object, and instead of an object, you're passing in a primitive type, or scalar (despite its NS-prefix, NSIntegeris not an object - just a typedefto a primitive value, and in your case, an int). What you need to do is wrap that scalar value in an object, and specifically, NSNumber, which is a class specifically designed to handle this.
这些错误意味着member:需要一个对象。id是指向 Objective-C 对象的指针，而不是对象，您传入的是原始类型或标量（尽管有NS-前缀，但它NSInteger不是对象 - 只是typedef原始值的 a，在您的情况下，是int）。您需要做的是将该标量值包装在一个对象中，特别NSNumber是 ，这是一个专门设计用于处理此问题的类。
Instead of calling member:with ASCIIValueOfLetter, you need to call it with the wrapped value, [NSNumber numberWithInteger:ASCIIValueOfLetter], as Maurício mentioned.
而不是调用的member:使用ASCIIValueOfLetter，你需要包装的价值来调用它，[NSNumber numberWithInteger:ASCIIValueOfLetter]如毛里西奥提及。
