ios 在目标 C 中进行比较 - ARC 不允许将“int”隐式转换为“id”
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Comparing in objective C - Implicit conversion of 'int' to 'id' is disallowed with ARC
提问by Mads K
I i'm getting the error "Implicit conversion of 'int' to 'id' is disallowed with ARC" at the line marked with "faulty line". I guess it have something to do with that i'm checking for an integer in an array, that contains objects instead of integers.
我在标有“故障行”的行收到错误“ARC 不允许将‘int’隐式转换为‘id’”。我想这与我正在检查数组中的整数有关，该数组包含对象而不是整数。
#import "RandomGenerator.h"
@implementation RandomGenerator
NSMutableArray *drawnNumbers;
-(int) randomNumber:(int)upperNumber {
return arc4random_uniform(upperNumber);
}
-(NSMutableArray*) lotteryNumbers :(int)withMaximumDrawnNumbers :(int)andHighestNumber {
for (int i = 1; i <= withMaximumDrawnNumbers; i++)
{
int drawnNumber = [self randomNumber:andHighestNumber];
if ([drawnNumbers containsObject:drawnNumber]) { //faulty line
//foo
}
}
return drawnNumbers;
}
@end
回答by manecosta
NSArrays can only contain objective-c objects. So actually the method containsObject:is expecting an object, not an int or any other primitive type.
NSArrays 只能包含objective-c 对象。所以实际上方法containsObject:期待一个对象，而不是 int 或任何其他原始类型。
If you want to store number inside an NSArray you should pack them into NSNumberobjects.
如果您想将数字存储在 NSArray 中，您应该将它们打包到NSNumber对象中。
NSNumber *someNumber = [NSNumber numberWithInt:3];
In your case, if we assume that drawnNumbers is already an array of NSNumbers, you should change the randomNumber:generation to:
在您的情况下，如果我们假设 drawNumbers 已经是一个 NSNumbers 数组，您应该将randomNumber:generation更改为：
-(NSNumber*) randomNumber:(int)upperNumber {
return [NSNumber numberWithInt:arc4random_uniform(upperNumber)];
}
And then when picking it up on the lotteryNumbers method, you should:
然后在使用 lotteryNumbers 方法时，您应该：
NSNumber *drawnNumber = [self randomNumber:andHighestNumber];
Another note would go for the method you defined for lotteryNumbers. You used a really strange name for it, I think you misunderstood how the method naming works in objective-c. You were probably looking for something more like:
另一个注释适用于您为 lotteryNumbers 定义的方法。您为它使用了一个非常奇怪的名称，我认为您误解了方法命名在objective-c 中的工作原理。您可能正在寻找更像的东西：
-(NSMutableArray*) lotteryNumbersWithMaximumDrawnNumbers:(int)maximumDrawnNumbers andHighestNumber:(int)highestNumber;
Late edit:
后期编辑：
Objective-C now allows a way more compact syntax for creating NSNumbers. You can do it like:
Objective-C 现在允许使用更紧凑的语法来创建 NSNumbers。你可以这样做：
NSNumber *someNumber = @(3);
And your method could be rewritten as:
你的方法可以改写为：
-(NSNumber*) randomNumber:(int)upperNumber {
return @(arc4random_uniform(upperNumber));
}
回答by Wain
You are using an intwhere an object (presumably NSNumber) is expected. So convert before use:
您正在使用一个int对象（大概是NSNumber）预期的地方。所以在使用前转换：
if ([drawnNumbers containsObject:@( drawnNumber )])
