iOS - 运行时动态 Class 不符合键值编码

Question

我一直在加快在 Objective-C 运行时创建动态 Class 的速度，并且遇到了一个我似乎无法完全解决的问题。找了好久，还是一头雾水。

这里的问题是：

[runtimeClassInstance setValue:age forKey:@"age"];

调用实例化对象：

id runtimeClassInstance = [[NSClassFromString(@"Employee") alloc] init];

创建者

[NewClassMaker buildClassFromDictionary:@[@"FirstName", @"LastName",\
                                          @"Age", @"Salary"]
                               withName:@"Employee"];

这是一个 NSUnknownKeyException：这个 class 不符合密钥年龄 错误的密钥值编码。

如果我使用以下调用方法，一切正常：

SEL setAgeSelector = NSSelectorFromString(@"setAge");
NSInvocation *call = [NSInvocation invocationWithMethodSignature:[[NSClassFromString(@"Employee") class] instanceMethodSignatureForSelector:setAgeSelector]];
call.target = runtimeClassInstance;
call.selector = setAgeSelector;
NSNumber *age = @(25);
[call setArgument:&age atIndex:2];
[call invoke];

现在创建 class 的静态方法是这样的：

+(NSDictionary*)buildClassFromDictionary:(NSArray*)propNames withName:(NSString*)className
{
    NSMutableDictionary* keys = [[NSMutableDictionary alloc]init];
    Class newClass = NSClassFromString(className);

    if(newClass == nil)
    {
        newClass = objc_allocateClassPair([NSObject class], [className UTF8String], 0);

        // For each property name, add a new iVar, getter, and setter method for it.
        for(NSString* key in propNames)
        {
            NSString* propName = [self propName: key];
            NSString* iVarName = [self ivarName:propName];

            class_addIvar(newClass, [iVarName UTF8String] , sizeof(NSObject*), log2(sizeof(NSObject*)), @encode(NSObject));

            objc_property_attribute_t a1 = { "T", "@\"NSObject\"" };
            objc_property_attribute_t a2 = { "&", "" };
            objc_property_attribute_t a3 = { "N", "" };
            objc_property_attribute_t a4 = { "V", [iVarName UTF8String] };
            objc_property_attribute_t attrs[] = { a1, a2, a3, a4};

            class_addProperty(newClass, [propName UTF8String], attrs, 4);
            class_addMethod(newClass, NSSelectorFromString(propName), (IMP)getter, "@@:");
            class_addMethod(newClass, NSSelectorFromString([self setterName:propName]), (IMP)setter, "v@:@");

            [keys setValue:key forKey:propName];
        }

        Class metaClass = object_getClass(newClass);
        // This method is returning NO on purpose to find out why there is no key.
        class_addMethod(metaClass, @selector(accessInstanceVariablesDirectly), (IMP)accessInstanceVariablesDirectly, "B@:");

        // Auxilliary methods added to the new class instance so the accessor dynamic methods above can work.
        // Not sure if the initial impl of this class maker class worked.
        class_addMethod(newClass, @selector(ivarName:), (IMP)ivarNameForString, "@@:@");
        class_addMethod(newClass, @selector(propName:), (IMP)propNameForString, "@@:@");
        class_addMethod(newClass, @selector(propNameFromSetterName:), (IMP)propNameFromSetterNameString, "@@:@");

        // Add a customized description dynamic method to this class. It will dump out any list of properties added
        // to the object during init here.
        Method description = class_getInstanceMethod([NSObject class],
                                                     @selector(description));
        const char *types = method_getTypeEncoding(description);

        // now add
        class_addMethod(newClass, @selector(description), (IMP)Description, types);
        objc_registerClassPair(newClass);
    }
    return keys;
}

我正在考虑三种可能性：

我在这里错过了获取这些属性的一些关键步骤他们的动态访问器以兼容键值的方式工作
如果我允许直接 iVar 访问，是否保留值发生了什么？
NSInvocation 方法是最好的方法吗？

Answer 1

setter 方法被命名为 setAge。 setValue:forKey: 搜索带冒号的 setAge:。在 setter 方法的名称末尾添加一个冒号。在 Objective-C 中，冒号是方法名称的一部分。

iOS - 运行时动态 Class 不符合键值编码

iOS - Runtime Dynamic Class not key-value coding compliant

dynamic

objective-c

key-value-coding