iOS使用系统数字键盘闪退 UIKeyboardTypeNumberPad

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSDictionaryM __setObject:forKey:]: object cannot be nil (key: NSFont)'

1.代码如下：

    UITextField *fieldText = [[UITextField alloc] initWithFrame:CGRectMake( 30, 120, 200, 25)];
    fieldText.placeholder = @"请输入手机号";
    fieldText.keyboardType  = UIKeyboardTypeNumberPad;
    fieldText.clearButtonMode = UITextFieldViewModeWhileEditing;
    fieldText.font = [UIFont systemFontOfSize:16];
    [self.view addSubview: fieldText];

2.报错如下：

Terminating app due to uncaught exception
 'NSInvalidArgumentException', 
reason: '*** -[__NSDictionaryM __setObject:forKey:]: 
object cannot be nil (key: NSFont)'

3.描述

将键盘模式设置成:
UIKeyboardTypeDefault
UIKeyboardTypeNumbersAndPunctuation
都可以使用，但是使用UIKeyboardTypeNumberPad闪退。
(按键1、2、3..闪退，按键0不闪退)
报错信息啥也看不出来。。。。

4.解决问题：

后来发现是项目中有一个UIFont+ETExtension的扩展类
，里边使用了方法交换。具体问题暂时没有发现。但是注释了方法交换后就没事儿了。还在继续钻研中。

+ (void)swizzleFontMethod {
    
    if (isIOS11) {
        // 交换systemFont
        Method originalMethod = class_getClassMethod(self, @selector(systemFontOfSize:));
        Method swizzledMethod = class_getClassMethod(self, @selector(et_systemFontOfSize:));
        method_exchangeImplementations(originalMethod, swizzledMethod);
        
        // 交换boldFont
        originalMethod = class_getClassMethod(self, @selector(boldSystemFontOfSize:));
        swizzledMethod = class_getClassMethod(self, @selector(et_boldFontOfSize:));
        method_exchangeImplementations(originalMethod, swizzledMethod);
        
        // 交换systemFontOfSize:weight:
        originalMethod = class_getClassMethod(self, @selector(systemFontOfSize:weight:));
        swizzledMethod = class_getClassMethod(self, @selector(et_systemFontOfSize:weight:));
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
   
}

+ (UIFont *)et_systemFontOfSize:(CGFloat)fontSize {
    return [UIFont fontWithName:PingFang_SC_Regular size:fontSize];
}

+ (UIFont *)et_boldFontOfSize:(CGFloat)fontSize {
    return [UIFont fontWithName:PingFang_SC_Bold size:fontSize];
}

+ (UIFont *)et_systemFontOfSize:(CGFloat)fontSize weight:(UIFontWeight)weight {
    // 根据weight 替换为 PingFang_SC字体的weight
    UIFont *font = [UIFont fontWithName:PingFang_SC_Regular size:fontSize];
    if (weight == UIFontWeightThin) {
        font = [UIFont fontWithName:PingFang_SC_Thin size:fontSize];
    } else if (weight == UIFontWeightLight) {
        font = [UIFont fontWithName:PingFang_SC_Light size:fontSize];
    } else if (weight == UIFontWeightMedium) {
        font = [UIFont fontWithName:PingFang_SC_Medium size:fontSize];
    } else if (weight == UIFontWeightSemibold) {
        font = [UIFont fontWithName:PingFang_SC_Semibold size:fontSize];
    } else if (weight == UIFontWeightBold) {
        font = [UIFont fontWithName:PingFang_SC_Bold size:fontSize];
    } else if (weight == UIFontWeightUltraLight) {
        font = [UIFont fontWithName:PingFang_SC_Ultralight size:fontSize];
    }
    return font;
}