iphone - 将 NSNumber 转换为 BOOL Objective-C

Question

我想将整数 0 和 1 转换为 BOOLEAN YES 和 NO

我的代码:

    NSNumber *num = 0;
    BOOL myBool = [num boolValue];
    NSLog(@"bool is: %@",myBool);

输出为 (null)

有什么问题吗？

Answer 1

首先，你的NSNumber的初始化是不正确的。您应该使用定义在 NSNumber:

上的 +numberWith: 类方法之一

+ (NSNumber *)numberWithChar:(char)value;
+ (NSNumber *)numberWithUnsignedChar:(unsigned char)value;
+ (NSNumber *)numberWithShort:(short)value;
+ (NSNumber *)numberWithUnsignedShort:(unsigned short)value;
+ (NSNumber *)numberWithInt:(int)value;
+ (NSNumber *)numberWithUnsignedInt:(unsigned int)value;
+ (NSNumber *)numberWithLong:(long)value;
+ (NSNumber *)numberWithUnsignedLong:(unsigned long)value;
+ (NSNumber *)numberWithLongLong:(long long)value;
+ (NSNumber *)numberWithUnsignedLongLong:(unsigned long long)value;
+ (NSNumber *)numberWithFloat:(float)value;
+ (NSNumber *)numberWithDouble:(double)value;
+ (NSNumber *)numberWithBool:(BOOL)value;
+ (NSNumber *)numberWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0);
+ (NSNumber *)numberWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0);

BOOL 只是 signed char，因此您不能使用 %@ 格式说明符，但您可以使用任何整数格式说明符，例如 %d、%i 或 %c。

但是，要输出YES 或NO，您需要使用字符串:

NSLog(@"bool is: %@", (myBool) ? @"YES" : @"NO");