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Posted on Edited on In

抛出问题

群友(@止一)昨晚上发了一个问题:

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typedef struct Test {
    NSArray *arr;
} Test;
- (void)test {
    Test test = {};
    test.arr = @[@1, @2, @3];
    self.var = test;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    [self test];
    for (int i = 0; i < 1000; i++) {
        NSLog(@"%@", self.var.arr);
    }

}

xcode12这样写会崩溃

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Posted on Edited on In

抛出问题

群友(@闲人)贴了这么一个会崩溃的代码:

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@implementation NSObject (test)
- (id)performSelector:(SEL)aSelector withObjects:(NSArray *)objects {

    NSMethodSignature *methodSignature = [[self class] instanceMethodSignatureForSelector:aSelector];
    // ...
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
    // ...
    [invocation invoke];
    //返回值处理
    id callBackObject = NULL;
    if(methodSignature.methodReturnLength) {
        [invocation getReturnValue:&callBackObject];
    }
    return callBackObject;
}
@end

@interface TestModel: NSObject
@property (nonatomic, strong) NSNumber *age;
@end
@implementation TestModel
- (instancetype)initWithA:(NSString *)a b:(NSString *)b c:(NSString *)c {
    if (self = [super init]) {
        printf("initABC\n");
    }
    return self;
}
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    TestModel *_teM;
    Class class = NSClassFromString(@"TestModel");
    _teM = [[class alloc] performSelector:@selector(initWithA:b:c:) withObjects:@[@"1",@"1",@"1"]];
    [_teM performSelector:@selector(setAge:) withObject:@1]; /*  <- EXC_BAD_ACCESS  */
    printf("over\n");
}
@end

对,段错误,代码挂在了[_teM performSelector:@selector(setAge:) withObject:@1]

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Posted on In

一个问题

  • Xcode: Version 11.4.1 (11E503a)
  • swift: Swift 5
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import UIKit
class MDButton: UIButton {
    // 为了更清楚展示问题,代码经过精简
    open class func make() -> Self {
        return MDButton()
    }
}

上面的代码无法编译:

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ViewController.swift: error: cannot convert return expression of type 'MDButton' to return type 'Self'
        return MDButton()
               ^~~~~~~~~~
                          as! Self
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