比较目标C - ARC不允许'int'到'id'的隐式转换 [英] Comparing in objective C - Implicit conversion of 'int' to 'id' is disallowed with ARC

问题描述

我得到的错误隐式转换'int'到'id'不允许与ARC标记为faulty line的行。我想它有一些与我在检查数组中的整数，包含对象而不是整数。有关。

  #importRandomGenerator.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]）{//错误的行
 // foo 
} 
} 
 return drawnNumbers; 
} 
 
 @end 
  

解决方案>

NSArrays只能包含目标c对象。所以实际上方法 containsObject：期望一个对象，而不是一个int或任何其他原始类型。

如果你想在一个NSArray您应该将它们打包到 NSNumber 对象中。

  NSNumber * someNumber = [NSNumber numberWithInt：3] ; 
  

在你的情况下，如果我们假设drawnNumbers已经是一个NSNumbers数组， strong> randomNumber：代为：

   - （NSNumber *）randomNumber：（int）upperNumber {
 return [NSNumber numberWithInt：arc4random_uniform（upperNumber）]; 
} 
  

然后当在lotteryNumbers方法上使用它时， p>

  NSNumber * drawnNumber = [self randomNumber：andHighestNumber]; 
  

另一个注释将针对您为lotteryNumbers定义的方法。你使用了一个非常奇怪的名字，我认为你误解了方法命名在objective-c中是如何工作的。你可能在寻找更像：

   - （NSMutableArray *）lotteryNumbersWithMaximumDrawnNumbers：（int）maximumDrawnNumbers andHighestNumber：（int）highestNumber ; 
  

晚期编辑：

$ b b

Objective-C现在允许一种更紧凑的语法来创建NSNumbers。你可以这样做：

  NSNumber * someNumber = @（3）;您的方法可以重写为：
 
  

- （NSNumber *）randomNumber：（int）upperNumber {
return @（arc4random_uniform（upperNumber））;
}


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.

#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

解决方案

NSArrays can only contain objective-c objects. So actually the method containsObject: is expecting an object, not an int or any other primitive type.

If you want to store number inside an NSArray you should pack them into NSNumber objects.

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:

-(NSNumber*) randomNumber:(int)upperNumber {
    return [NSNumber numberWithInt:arc4random_uniform(upperNumber)];
}

And then when picking it up on the lotteryNumbers method, you should:

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:

-(NSMutableArray*) lotteryNumbersWithMaximumDrawnNumbers:(int)maximumDrawnNumbers andHighestNumber:(int)highestNumber;

Late edit:

Objective-C now allows a way more compact syntax for creating NSNumbers. You can do it like:

NSNumber *someNumber = @(3);

And your method could be rewritten as:

-(NSNumber*) randomNumber:(int)upperNumber {
    return @(arc4random_uniform(upperNumber));
}

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