如何使用NSCoding保存Int64变量

@interface CustomClass : NSObject <NSCoding>

@property (nonatomic, assign) Int64 myInt64Variable;

@end

@implementation CustomClass

- (instancetype)initWithCoder:(NSCoder *)coder {
    self = [super init];
    if (self) {
        self.myInt64Variable = [coder decodeInt64ForKey:@"myInt64Variable"];
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeInt64:self.myInt64Variable forKey:@"myInt64Variable"];
}

@end

CustomClass *customObject = [[CustomClass alloc] init];
customObject.myInt64Variable = 1234567890;

NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).firstObject stringByAppendingPathComponent:@"customObject.dat"];
[NSKeyedArchiver archiveRootObject:customObject toFile:filePath];

CustomClass *savedObject = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
Int64 savedInt64Variable = savedObject.myInt64Variable;