【iOS】JSONModel源码阅读笔记 - IT评测·应用市场-qidao123.com技术社区

#import <JSONModel/JSONModel.h>
@interface UserProfile : JSONModel
@property (strong, nonatomic) NSString* userId;
@property (strong, nonatomic) NSString* emailAddress;
@property (strong, nonatomic) NSString* firstName;
@property (strong, nonatomic) NSString* lastName;
@end

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@implementation UserProfile
// 使用 JSONKeyMapper 来定义 JSON 字段与模型属性之间的映射关系
+ (JSONKeyMapper *)keyMapper {
return [[JSONKeyMapper alloc] initWithModelToJSONDictionary:@{
@"userId": @"user_id",
@"emailAddress": @"email_address",
@"firstName": @"profile_info.first_name",
@"lastName": @"profile_info.last_name"
}];
}
@end

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-(instancetype)initWithString:(NSString*)string error:(JSONModelError**)err;
-(instancetype)initWithString:(NSString *)string usingEncoding:(NSStringEncoding)encoding error:(JSONModelError**)err;
-(instancetype)initWithDictionary:(NSDictionary*)dict error:(NSError **)err;
-(instancetype)initWithData:(NSData *)data error:(NSError **)error;

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-(id)initWithDictionary:(NSDictionary*)dict error:(NSError**)err
{
//方法1. 参数为nil
if (!dict) {
if (err) *err = [JSONModelError errorInputIsNil];
return nil;
}
//方法2. 参数不是nil，但也不是字典
if (![dict isKindOfClass:[NSDictionary class]]) {
if (err) *err = [JSONModelError errorInvalidDataWithMessage:@"Attempt to initialize JSONModel object using initWithDictionary:error: but the dictionary parameter was not an 'NSDictionary'."];
return nil;
}
//方法3. 初始化
self = [self init];
if (!self) {
//初始化失败
if (err) *err = [JSONModelError errorModelIsInvalid];
return nil;
}
//方法4. 检查用户定义的模型里的属性集合是否大于传入的字典里的key集合（如果大于，则返回NO）
if (![self __doesDictionary:dict matchModelWithKeyMapper:self.__keyMapper error:err]) {
return nil;
}
//方法5. 核心方法：字典的key与模型的属性的映射
if (![self __importDictionary:dict withKeyMapper:self.__keyMapper validation:YES error:err]) {
return nil;
}
//方法6. 可以重写[self validate:err]方法并返回NO，让用户自定义错误并阻拦model的返回
if (![self validate:err]) {
return nil;
}
//方法7. 终于通过了！成功返回model
return self;
}

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self = [self init];
if (!self) {
//super init didn't succeed
if (err) *err = [JSONModelError errorModelIsInvalid];
return nil;
}

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- (id)init
{
self = [super init];
if (self) {
//do initial class setup
[self __setup__];
}
return self;
}

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- (void)__setup__
{
//if first instance of this model, generate the property list
// 如果是该模型的第一个实例，则生成属性列表
if (!objc_getAssociatedObject(self.class, &kClassPropertiesKey)) {
[self __inspectProperties];
}
//if there's a custom key mapper, store it in the associated object
id mapper = [[self class] keyMapper];
if ( mapper && !objc_getAssociatedObject(self.class, &kMapperObjectKey) ) {
objc_setAssociatedObject(
self.class,
&kMapperObjectKey,
mapper,
OBJC_ASSOCIATION_RETAIN // This is atomic
);
}
}

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if ( mapper && !objc_getAssociatedObject(self.class, &kMapperObjectKey) ) {
objc_setAssociatedObject(
self.class,
&kMapperObjectKey,
mapper,
OBJC_ASSOCIATION_RETAIN // This is atomic
);
}

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-(void)__inspectProperties
{
// 最终保存所有属性的字典，形式为：
// {
// age = "@property primitive age (Setters = [])";
// friends = "@property NSArray* friends (Standard JSON type, Setters = [])";
// gender = "@property NSString* gender (Standard JSON type, Setters = [])";
// name = "@property NSString* name (Standard JSON type, Setters = [])";
// }
NSMutableDictionary* propertyIndex = [NSMutableDictionary dictionary];
//获取当前的类名
Class class = [self class];
NSScanner* scanner = nil;
NSString* propertyType = nil;
// 循环条件：当class 是 JSONModel自己的时候终止
while (class != [JSONModel class]) {
//属性的个数
unsigned int propertyCount;
//获得属性列表（所有@property声明的属性）
objc_property_t *properties = class_copyPropertyList(class, &propertyCount);
//遍历所有的属性
for (unsigned int i = 0; i < propertyCount; i++) {
//获得属性名称
objc_property_t property = properties[i];//获得当前的属性
const char *propertyName = property_getName(property);//name（C字符串）
//JSONModel里的每一个属性，都被封装成一个JSONModelClassProperty对象
JSONModelClassProperty* p = [[JSONModelClassProperty alloc] init];
p.name = @(propertyName);//propertyName:属性名称，例如：name，age，gender
//获得属性类型
const char *attrs = property_getAttributes(property);
NSString* propertyAttributes = @(attrs);
// T@"NSString",C,N,V_name
// Tq,N,V_age
// T@"NSString",C,N,V_gender
// T@"NSArray",&,N,V_friends
NSArray* attributeItems = [propertyAttributes componentsSeparatedByString:@","];
//说明是只读属性，不做任何操作
if ([attributeItems containsObject:@"R"]) {
continue; //to next property
}
//检查出是布尔值
if ([propertyAttributes hasPrefix:@"Tc,"]) {
p.structName = @"BOOL";//使其变为结构体
}
//实例化一个scanner
scanner = [NSScanner scannerWithString: propertyAttributes];
[scanner scanUpToString:@"T" intoString: nil];
[scanner scanString:@"T" intoString:nil];
//http://blog.csdn.net/kmyhy/article/details/8258858
if ([scanner scanString:@"@"" intoString: &propertyType]) {
//属性是一个对象
[scanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@""<"]
intoString:&propertyType];//propertyType -> NSString
p.type = NSClassFromString(propertyType);// p.type = @"NSString"
p.isMutable = ([propertyType rangeOfString:@"Mutable"].location != NSNotFound); //判断是否是可变的对象
p.isStandardJSONType = [allowedJSONTypes containsObject:p.type];//是否是该框架兼容的类型
//存在协议(数组，也就是嵌套模型)
while ([scanner scanString:@"<" intoString:NULL]) {
NSString* protocolName = nil;
[scanner scanUpToString:@">" intoString: &protocolName];
if ([protocolName isEqualToString:@"Optional"]) {
p.isOptional = YES;
} else if([protocolName isEqualToString:@"Index"]) {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
p.isIndex = YES;
#pragma GCC diagnostic pop
objc_setAssociatedObject(
self.class,
&kIndexPropertyNameKey,
p.name,
OBJC_ASSOCIATION_RETAIN // This is atomic
);
} else if([protocolName isEqualToString:@"Ignore"]) {
p = nil;
} else {
p.protocol = protocolName;
}
//到最接近的>为止
[scanner scanString:@">" intoString:NULL];
}
}
else if ([scanner scanString:@"{" intoString: &propertyType])
//属性是结构体
[scanner scanCharactersFromSet:[NSCharacterSet alphanumericCharacterSet]
intoString:&propertyType];
p.isStandardJSONType = NO;
p.structName = propertyType;
}
else {
//属性是基本类型：Tq,N,V_age
[scanner scanUpToCharactersFromSet:[NSCharacterSet characterSetWithCharactersInString:@","]
intoString:&propertyType];
//propertyType:q
propertyType = valueTransformer.primitivesNames[propertyType];
//propertyType:long
//基本类型数组
if (![allowedPrimitiveTypes containsObject:propertyType]) {
//类型不支持
@throw [NSException exceptionWithName:@"JSONModelProperty type not allowed"
reason:[NSString stringWithFormat:@"Property type of %@.%@ is not supported by JSONModel.", self.class, p.name]
userInfo:nil];
}
}
NSString *nsPropertyName = @(propertyName);
//可选的
if([[self class] propertyIsOptional:nsPropertyName]){
p.isOptional = YES;
}
//可忽略的
if([[self class] propertyIsIgnored:nsPropertyName]){
p = nil;
}
//集合类
Class customClass = [[self class] classForCollectionProperty:nsPropertyName];
if (customClass) {
p.protocol = NSStringFromClass(customClass);
}
//忽略block
if ([propertyType isEqualToString:@"Block"]) {
p = nil;
}
//如果字典里不存在，则添加到属性字典里（终于添加上去了。。。）
if (p && ![propertyIndex objectForKey:p.name]) {
[propertyIndex setValue:p forKey:p.name];
}
//setter 和 getter
if (p)
{ //name ->Name
NSString *name = [p.name stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:[p.name substringToIndex:1].uppercaseString];
// getter
SEL getter = NSSelectorFromString([NSString stringWithFormat:@"JSONObjectFor%@", name]);
if ([self respondsToSelector:getter])
p.customGetter = getter;
// setters
p.customSetters = [NSMutableDictionary new];
SEL genericSetter = NSSelectorFromString([NSString stringWithFormat:@"set%@WithJSONObject:", name]);
if ([self respondsToSelector:genericSetter])
p.customSetters[@"generic"] = [NSValue valueWithBytes:&genericSetter objCType:@encode(SEL)];
for (Class type in allowedJSONTypes)
{
NSString *class = NSStringFromClass([JSONValueTransformer classByResolvingClusterClasses:type]);
if (p.customSetters[class])
continue;
SEL setter = NSSelectorFromString([NSString stringWithFormat:@"set%@With%@:", name, class]);
if ([self respondsToSelector:setter])
p.customSetters[class] = [NSValue valueWithBytes:&setter objCType:@encode(SEL)];
}
}
}
free(properties);
//再指向自己的父类，知道等于JSONModel才停止
class = [class superclass];
}
//最后保存所有当前类，JSONModel的所有的父类的属性
objc_setAssociatedObject(
self.class,
&kClassPropertiesKey,
[propertyIndex copy],
OBJC_ASSOCIATION_RETAIN
);
}

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objc_property_t *properties = class_copyPropertyList(class, &propertyCount);

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JSONModelClassProperty* p = [[JSONModelClassProperty alloc] init];

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if (p && ![propertyIndex objectForKey:p.name]) {
[propertyIndex setValue:p forKey:p.name];
}

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p.type = NSClassFromString(propertyType);
p.isMutable = ([propertyType rangeOfString:@"Mutable"].location != NSNotFound);
p.isStandardJSONType = [allowedJSONTypes containsObject:p.type];

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//最后保存所有当前类，JSONModel的所有的父类的属性
objc_setAssociatedObject(
self.class,
&kClassPropertiesKey,
[propertyIndex copy],
OBJC_ASSOCIATION_RETAIN
);

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while (class != [JSONModel class]) {
......................
......................
class = [class superclass];
}

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//model类里面定义的属性集合是不能大于传入的字典里的key集合的。
//如果存在了用户自定义的mapper，则需要按照用户的定义来进行转换。
//（例如将gender转换为了sex）。
-(BOOL)__doesDictionary:(NSDictionary*)dict matchModelWithKeyMapper:(JSONKeyMapper*)keyMapper error:(NSError**)err
{
//check if all required properties are present
//拿到字典里所有的key
NSArray* incomingKeysArray = [dict allKeys];
NSMutableSet* requiredProperties = [self __requiredPropertyNames].mutableCopy;
//从array拿到set
NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray];
//transform the key names, if necessary
//如有必要，变换键名称
//如果用户自定义了mapper，则进行转换
if (keyMapper || globalKeyMapper) {
NSMutableSet* transformedIncomingKeys = [NSMutableSet setWithCapacity: requiredProperties.count];
NSString* transformedName = nil;
//loop over the required properties list
//在所需属性列表上循环
//遍历需要转换的属性列表
for (JSONModelClassProperty* property in [self __properties__])
{
//被转换成的属性名称（例如）TestModel（模型内） -> url（字典内）
transformedName = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper] : property.name;
//check if exists and if so, add to incoming keys
//检查是否存在，如果存在，则添加到传入密钥
//（例如）拿到url以后，查看传入的字典里是否有url对应的值
id value;
@try {
value = [dict valueForKeyPath:transformedName];
}
@catch (NSException *exception) {
value = dict[transformedName];
}
if (value) {
[transformedIncomingKeys addObject: property.name];
}
}
//overwrite the raw incoming list with the mapped key names
//用映射的键名称覆盖原始传入列表
incomingKeys = transformedIncomingKeys;
}
//check for missing input keys
//检查是否缺少输入键
//查看当前的model的属性的集合是否大于传入的属性集合，如果是，则返回错误
//也就是说模型类里的属性是不能多于传入字典里的key的，例如：
if (![requiredProperties isSubsetOfSet:incomingKeys]) {
//get a list of the missing properties
//获取缺失属性的列表（获取多出来的属性）
[requiredProperties minusSet:incomingKeys];
//not all required properties are in - invalid input
//并非所有必需的属性都在 in - 输入无效
JMLog(@"Incoming data was invalid [%@ initWithDictionary:]. Keys missing: %@", self.class, requiredProperties);
if (err) *err = [JSONModelError errorInvalidDataWithMissingKeys:requiredProperties];
return NO;
}
//not needed anymore
//不再需要了，释放掉
incomingKeys= nil;
requiredProperties= nil;
return YES;
}

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NSArray* incomingKeysArray = [dict allKeys];

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NSMutableSet* requiredProperties = [self __requiredPropertyNames].mutableCopy;

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-(NSMutableSet*)__requiredPropertyNames
{
//fetch the associated property names
NSMutableSet* classRequiredPropertyNames = objc_getAssociatedObject(self.class, &kClassRequiredPropertyNamesKey);
if (!classRequiredPropertyNames) {
classRequiredPropertyNames = [NSMutableSet set];
[[self __properties__] enumerateObjectsUsingBlock:^(JSONModelClassProperty* p, NSUInteger idx, BOOL *stop) {
if (!p.isOptional) [classRequiredPropertyNames addObject:p.name];
}];
//persist the list
objc_setAssociatedObject(
self.class,
&kClassRequiredPropertyNamesKey,
classRequiredPropertyNames,
OBJC_ASSOCIATION_RETAIN // This is atomic
);
}
return classRequiredPropertyNames;
}

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NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray];

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transformedName = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper] : property.name;

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incomingKeys = transformedIncomingKeys;

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//check for missing input keys
if (![requiredProperties isSubsetOfSet:incomingKeys]) {
//get a list of the missing properties
[requiredProperties minusSet:incomingKeys];
//not all required properties are in - invalid input
JMLog(@"Incoming data was invalid [%@ initWithDictionary:]. Keys missing: %@", self.class, requiredProperties);
if (err) *err = [JSONModelError errorInvalidDataWithMissingKeys:requiredProperties];
return NO;
}

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//作者在最后给属性赋值的时候使用的是kvc的setValue:ForKey:的方法。
//作者判断了模型里的属性的类型是否是JSONModel的子类，可见作者的考虑是非常周全的。
//整个框架看下来，有很多的地方涉及到了错误判断，作者将将错误类型单独抽出一个类（JSONModelError），里面支持的错误类型很多，可以侧面反应作者思维之缜密。而且这个做法也可以在我们写自己的框架或者项目中使用。
//从字典里获取值并赋给当前模型对象
-(BOOL)__importDictionary:(NSDictionary*)dict withKeyMapper:(JSONKeyMapper*)keyMapper validation:(BOOL)validation error:(NSError**)err
{
//loop over the incoming keys and set self's properties
//遍历保存的所有属性的字典
for (JSONModelClassProperty* property in [self __properties__])
{
//convert key name to model keys, if a mapper is provided
//将属性的名称（若有改动就拿改后的名称）拿过来，作为key，用这个key来查找传进来的字典里对应的值
NSString* jsonKeyPath = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper] : property.name;
//JMLog(@"keyPath: %@", jsonKeyPath);
//general check for data type compliance
//用来保存从字典里获取的值
id jsonValue;
@try {
jsonValue = [dict valueForKeyPath: jsonKeyPath];
}
@catch (NSException *exception) {
jsonValue = dict[jsonKeyPath];
}
//check for Optional properties
//检查可选属性
//字典不存在对应的key
if (isNull(jsonValue)) {
//skip this property, continue with next property
//跳过此属性，继续下一个属性
//如果这个key是可以不存在的
if (property.isOptional || !validation) continue;
//如果这个key是必须有的，则返回错误
if (err) {
//null value for required property
//所需属性的值为null
NSString* msg = [NSString stringWithFormat:@"Value of required model key %@ is null", property.name];
JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg];
*err = [dataErr errorByPrependingKeyPathComponent:property.name];
}
return NO;
}
//获取，取到的值的类型
Class jsonValueClass = [jsonValue class];
BOOL isValueOfAllowedType = NO;
//查看是否是本框架兼容的属性类型
for (Class allowedType in allowedJSONTypes) {
if ( [jsonValueClass isSubclassOfClass: allowedType] ) {
isValueOfAllowedType = YES;
break;
}
}
//如果不兼容，则返回NO，mapping失败，抛出错误
if (isValueOfAllowedType==NO) {
//type not allowed
JMLog(@"Type %@ is not allowed in JSON.", NSStringFromClass(jsonValueClass));
if (err) {
NSString* msg = [NSString stringWithFormat:@"Type %@ is not allowed in JSON.", NSStringFromClass(jsonValueClass)];
JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg];
*err = [dataErr errorByPrependingKeyPathComponent:property.name];
}
return NO;
}
//check if there's matching property in the model
//检查模型中是否有匹配的属性
//如果是兼容的类型：
if (property) {
// check for custom setter, than the model doesn't need to do any guessing
// how to read the property's value from JSON
//检查自定义setter，则模型不需要进行任何猜测（查看是否有自定义setter，并设置）
//如何从JSON读取属性值
if ([self __customSetValue:jsonValue forProperty:property]) {
//skip to next JSON key
//跳到下一个JSON键
continue;
};
// 0) handle primitives
//0）句柄原语
//基本类型
if (property.type == nil && property.structName==nil) {
//generic setter
//通用setter
//kvc赋值
if (jsonValue != [self valueForKey:property.name]) {
[self setValue:jsonValue forKey: property.name];
}
//skip directly to the next key
//直接跳到下一个键
continue;
}
// 0.5) handle nils
//如果传来的值是空，即使当前的属性对应的值不是空，也要将空值赋给它
if (isNull(jsonValue)) {
if ([self valueForKey:property.name] != nil) {
[self setValue:nil forKey: property.name];
}
continue;
}
// 1) check if property is itself a JSONModel
//检查属性本身是否是jsonmodel类型
if ([self __isJSONModelSubClass:property.type]) {
//initialize the property's model, store it
//初始化属性的模型，并将其存储
//通过自身的转模型方法，获取对应的值
JSONModelError* initErr = nil;
id value = [[property.type alloc] initWithDictionary: jsonValue error:&initErr];
if (!value) {
//skip this property, continue with next property
//跳过此属性，继续下一个属性（如果该属性不是必须的，则略过）
if (property.isOptional || !validation) continue;
// Propagate the error, including the property name as the key-path component
//传播错误，包括将属性名称作为密钥路径组件（如果该属性是必须的，则返回错误）
if((err != nil) && (initErr != nil))
{
*err = [initErr errorByPrependingKeyPathComponent:property.name];
}
return NO;
}
//当前的属性值与value不同时，则赋值
if (![value isEqual:[self valueForKey:property.name]]) {
[self setValue:value forKey: property.name];
}
//for clarity, does the same without continue
//为清楚起见，不继续执行相同操作
continue;
} else {
// 2) check if there's a protocol to the property
// ) might or not be the case there's a built in transform for it
//2）检查是否有协议
//）可能是，也可能不是，它有一个内置的转换
if (property.protocol) {
//JMLog(@"proto: %@", p.protocol);
//转化为数组，这个数组就是例子中的friends属性
jsonValue = [self __transform:jsonValue forProperty:property error:err];
if (!jsonValue) {
if ((err != nil) && (*err == nil)) {
NSString* msg = [NSString stringWithFormat:@"Failed to transform value, but no error was set during transformation. (%@)", property];
JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg];
*err = [dataErr errorByPrependingKeyPathComponent:property.name];
}
return NO;
}
}
// 3.1) handle matching standard JSON types
//3.1）句柄匹配标准JSON类型
//对象类型
if (property.isStandardJSONType && [jsonValue isKindOfClass: property.type]) {
//mutable properties
//可变类型的属性
if (property.isMutable) {
jsonValue = [jsonValue mutableCopy];
}
//set the property value
//为属性赋值
if (![jsonValue isEqual:[self valueForKey:property.name]]) {
[self setValue:jsonValue forKey: property.name];
}
continue;
}
// 3.3) handle values to transform
//3.3）处理要转换的值
//当前的值的类型与对应的属性的类型不一样的时候，需要查看用户是否自定义了转换器（例如从NSSet到NSArray转换：-(NSSet *)NSSetFromNSArray:(NSArray *)array）
if (
(![jsonValue isKindOfClass:property.type] && !isNull(jsonValue))
||
//the property is mutable
//属性是可变的
property.isMutable
||
//custom struct property
//自定义结构属性
property.structName
) {
// searched around the web how to do this better
// but did not find any solution, maybe that's the best idea? (hardly)
//在网上搜索如何更好地做到这一点
//但是没有找到任何解决方案，也许这是最好的主意？（几乎没有）
Class sourceClass = [JSONValueTransformer classByResolvingClusterClasses:[jsonValue class]];
//JMLog(@"to type: [%@] from type: [%@] transformer: [%@]", p.type, sourceClass, selectorName);
//build a method selector for the property and json object classes
//为属性和json对象类构建方法选择器
NSString* selectorName = [NSString stringWithFormat:@"%@From%@:",
(property.structName? property.structName : property.type), //target name目标名
sourceClass]; //source name源名称
SEL selector = NSSelectorFromString(selectorName);
//check for custom transformer
//查看自定义的转换器是否存在
BOOL foundCustomTransformer = NO;
if ([valueTransformer respondsToSelector:selector]) {
foundCustomTransformer = YES;
} else {
//try for hidden custom transformer
//尝试隐藏自定义转换器
selectorName = [NSString stringWithFormat:@"__%@",selectorName];
selector = NSSelectorFromString(selectorName);
if ([valueTransformer respondsToSelector:selector]) {
foundCustomTransformer = YES;
}
}
//check if there's a transformer with that name
//检查是否有同名变压器
//如果存在自定义转换器，则进行转换
if (foundCustomTransformer) {
IMP imp = [valueTransformer methodForSelector:selector];
id (*func)(id, SEL, id) = (void *)imp;
jsonValue = func(valueTransformer, selector, jsonValue);
if (![jsonValue isEqual:[self valueForKey:property.name]])
[self setValue:jsonValue forKey:property.name];
} else {
//如果没有自定义转换器，返回错误
if (err) {
NSString* msg = [NSString stringWithFormat:@"%@ type not supported for %@.%@", property.type, [self class], property.name];
JSONModelError* dataErr = [JSONModelError errorInvalidDataWithTypeMismatch:msg];
*err = [dataErr errorByPrependingKeyPathComponent:property.name];
}
return NO;
}
} else {
// 3.4) handle "all other" cases (if any)
//3.4）处理“所有其他”情况（如有）
if (![jsonValue isEqual:[self valueForKey:property.name]])
[self setValue:jsonValue forKey:property.name];
}
}
}
}
return YES;
}

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for (JSONModelClassProperty* property in [self __properties__])

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NSString* jsonKeyPath = (keyMapper||globalKeyMapper) ? [self __mapString:property.name withKeyMapper:keyMapper] : property.name;

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id jsonValue;
@try {
jsonValue = [dict valueForKeyPath: jsonKeyPath];
}
@catch (NSException *exception) {
jsonValue = dict[jsonKeyPath];
}

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if (property.type == nil && property.structName==nil) {
//generic setter
//通用setter
//kvc赋值
if (jsonValue != [self valueForKey:property.name]) {
[self setValue:jsonValue forKey: property.name];
}
//skip directly to the next key
//直接跳到下一个键
continue;
}

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if (jsonValue != [self valueForKey:property.name]) {
[self setValue:jsonValue forKey: property.name];

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@interface User : JSONModel
@property (strong, nonatomic) NSString *userId;
@property (strong, nonatomic) NSString *email;
@property (strong, nonatomic) NSString *userDescription;
@end
@implementation User
+ (JSONKeyMapper *)keyMapper {
return [[JSONKeyMapper alloc] initWithModelToJSONDictionary:@{
@"userId": @"id",
@"email": @"email_address",
@"userDescription": @"description"
}];
}
@end

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