正文
JSONModel是一个解析服务器返回的Json数据的库。
通常服务器传回的json数据要通过写一个数据转换模块将NSDictionary转换为Model，将NSString数据转换为Model中property的数据类型。
这样服务器如果要做修改，可能需要改两三个文件。
JSONModel的出现就是为了将这种解析工作在设计层面完成。
使用方法：参考连接
对其源码的核心部分JSONModel.m做了源码阅读，笔记如下：
在
-(id)initWithDictionary:(NSDictionary*)dict error:(NSError**)err
函数中完成所有解析工作：如果有任何失误或者错误直接返回nil。
-(id)initWithDictionary:(NSDictionary*)dict error:(NSError**)err
{
//1、做有效性判断（dict是不是空啊，dict是不是真是一个NSDictionary）
//check for nil input
if (!dict) {
if (err) *err = [JSONModelError errorInputIsNil];
return nil;
}
//invalid input, just create empty instance
if (![dict isKindOfClass:[NSDictionary class]]) {
if (err) *err = [JSONModelError errorInvalidData];
return nil;
}
//create a class instance
self = [super init];
if (!self) {
//super init didn't succeed
if (err) *err = [JSONModelError errorModelIsInvalid];
return nil;
}
//__setup__中通过调用__restrospectProperties建立类属性的映射表，并且存放在全局变量classProperties里面
//->__restrospectProperties中利用runtime function搞出属性列表：
// ->获得属性列表class_copyPropertyList(得到objc_property_t数组)->对于每一个objc_property_t调用property_getName获得名称，property_getAttributes获得属性的描述（字符串）->通过解析字符串获得属性的类型、是否是Mutable、是否是基本的JSON类型等等
// ->调用[class superclass]获得父类继续获取列表
// ->列表保存在classProperties中备用
//->调用+keyMapper获得key转换列表，生成JSONKeyMapper对象存入keyMapper。
//do initial class setup, retrospec properties
[self __setup__];
//看看必传参数中是否在输入参数中都有。
//check if all required properties are present
NSArray* incomingKeysArray = [dict allKeys];
NSMutableSet* requiredProperties = [self __requiredPropertyNames];
NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray];
//get the key mapper
JSONKeyMapper* keyMapper = keyMappers[__className_];
//transform the key names, if neccessary
if (keyMapper) {
//对比dict输入的keyName导入NSSet与keyMapper中JSONKeyMapper对象做keyName的转换。统一转换为对象的propertyname。
NSMutableSet* transformedIncomingKeys = [NSMutableSet setWithCapacity: requiredProperties.count];
NSString* transformedName = nil;
//loop over the required properties list
for (NSString* requiredPropertyName in requiredProperties) {
//get the mapped key path
transformedName = keyMapper.modelToJSONKeyBlock(requiredPropertyName);
//chek if exists and if so, add to incoming keys
if ([dict valueForKeyPath:transformedName]) {
[transformedIncomingKeys addObject: requiredPropertyName];
}
}
//overwrite the raw incoming list with the mapped key names
incomingKeys = transformedIncomingKeys;
}
//利用NSSet的isSubsetOfSet:将必传参数表与输入的keyName表对比。如果不是包含关系说明参数传的不够。
//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._className_, requiredProperties);
if (err) *err = [JSONModelError errorInvalidDataWithMissingKeys:requiredProperties];
return nil;
}
//not needed anymore
incomingKeys= nil;
requiredProperties= nil;
//从对象的classProperties列表中循环到dict中取值：（赋值使用KVO操作的setValue:forKey:来做的，这样会直接调用setter函数赋值）
//loop over the incoming keys and set self's properties
for (JSONModelClassProperty* property in [self __properties__]) {
//对于每一个对象的property，通过keyMapper的转换找到对应dict property的dictKeyPath，找到值jsonValue。如果没有值，并且这个属性是Optional的就进行下一项property对比。
//convert key name ot model keys, if a mapper is provided
NSString* jsonKeyPath = property.name;
if (keyMapper) jsonKeyPath = keyMapper.modelToJSONKeyBlock( property.name );
//JMLog(@"keyPath: %@", jsonKeyPath);
//general check for data type compliance
id jsonValue = [dict valueForKeyPath: jsonKeyPath];
//check for Optional properties
if (jsonValue==nil && property.isOptional==YES) {
//skip this property, continue with next property
continue;
}
//对找到的值做类型判断，如果不是JSON应该返回的数据类型就报错。（注意：NSNull是可以作为参数回传的）
Class jsonValueClass = [jsonValue class];
BOOL isValueOfAllowedType = NO;
for (Class allowedType in allowedJSONTypes) {
if ( [jsonValueClass isSubclassOfClass: allowedType] ) {
isValueOfAllowedType = YES;
break;
}
}
if (isValueOfAllowedType==NO) {
//type not allowed
JMLog(@"Type %@ is not allowed in JSON.", NSStringFromClass(jsonValueClass));
if (err) *err = [JSONModelError errorInvalidData];
return nil;
}
//check if there's matching property in the model
//JSONModelClassProperty* property = classProperties[self.className][key];
//接着对property的属性与jsonValue进行类型匹配：
if (property) {
//如果是基本类型（int/float等）直接值拷贝；
// 0) handle primitives
if (property.type == nil && property.structName==nil) {
//just copy the value
[self setValue:jsonValue forKey: property.name];
//skip directly to the next key
continue;
}
//如果是NSNull直接赋空值；
// 0.5) handle nils
if (isNull(jsonValue)) {
[self setValue:nil forKey: property.name];
continue;
}
//如果是值也是一个JsonModel，递归搞JsonModel
// 1) check if property is itself a JSONModel
if ([[property.type class] isSubclassOfClass:[JSONModel class]]) {
//initialize the property's model, store it
NSError* initError = nil;
id value = [[property.type alloc] initWithDictionary: jsonValue error:&initError];
if (!value) {
if (initError && err) *err = [JSONModelError errorInvalidData];
return nil;
}
[self setValue:value forKey: property.name];
//for clarity, does the same without continue
continue;
} else {
//如果property中有protocol解析将jsonValue按照protocol解析，如NSArray<JsonModelSubclass>，protocol就是JsonModelSubclass
// 2) check if there's a protocol to the property
// ) might or not be the case there's a built in transofrm for it
if (property.protocol) {
//JMLog(@"proto: %@", p.protocol);
//__transform:forProperty:函数功能：
// ->先判断下protocolClass是否在运行环境中存在，如不存在并且property是NSArray类型，直接报错。否则，直接返回。
// ->如果protocalClass是JsonModel的子类，
// ->如果property.type是NSArray
//
->判断一下是否是使用时转换
//
->如果为使用时转换则输出一个JSONModelArray(NSArray)的子类
//
->如果不是使用时转换则输出一个NSArray，其中的对象全部转换为protocalClass所对应对象
// ->如果property.type是NSDictionary
//
->将value转换为protocalClass所对应对象
//
->根据key存储到一个NSDictionary中输出
jsonValue = [self __transform:jsonValue forProperty:property];
if (!jsonValue) {
if (err) *err = [JSONModelError errorInvalidData];
return nil;
}
}
//如果是基本JSON类型（NSString/NSNumber）
// 3.1) handle matching standard JSON types
if (property.isStandardJSONType && [jsonValue isKindOfClass: property.type]) {
//如果是mutable的，做一份MutableCopy
//mutable properties
if (property.isMutable) {
jsonValue = [jsonValue mutableCopy];
}
//set the property value
[self setValue:jsonValue forKey: property.name];
continue;
}
//如果property.type是NSArray
// 3.3) handle values to transform
if (
//如果（类型没有匹配，并且jsonValue不为空）或者是Mutable的property（说明是特殊类型转换）
(![jsonValue isKindOfClass:property.type] && !isNull(jsonValue))
||
//the property is mutable
property.isMutable
) {
//利用JSONValueTransformer找到源类型
// searched around the web how to do this better
// but did not find any solution, maybe that's the best idea? (hardly)
Class sourceClass = [JSONValueTransformer classByResolvingClusterClasses:[jsonValue class]];
//JMLog(@"to type: [%@] from type: [%@] transformer: [%@]", p.type, sourceClass, selectorName);
//用字符串拼出转换函数的名称字符串，到JSONValueTransformer中去搜索@SEL执行出正确类型
//build a method selector for the property and json object classes
NSString* selectorName = [NSString stringWithFormat:@"%@From%@:",
(property.structName? property.structName : property.type), //target name
sourceClass]; //source name
SEL selector = NSSelectorFromString(selectorName);
//check if there's a transformer with that name
if ([valueTransformer respondsToSelector:selector]) {
//it's OK, believe me...
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
//transform the value
jsonValue = [valueTransformer performSelector:selector withObject:jsonValue];
#pragma clang diagnostic pop
[self setValue:jsonValue forKey: property.name];
} else {
// it's not a JSON data type, and there's no transformer for it
// if property type is not supported - that's a programmer mistaked -> exception
@throw [NSException exceptionWithName:@"Type not allowed"
reason:[NSString stringWithFormat:@"%@ type not supported for %@.%@", property.type, [self class], property.name]
userInfo:nil];
return nil;
}
} else {
//哪儿都不是的直接存起来
// 3.4) handle "all other" cases (if any)
[self setValue:jsonValue forKey: property.name];
}
}
}
}
//最后调用validate:看看结果是不是有效，没问题就返回了。
//run any custom model validation
NSError* validationError = nil;
BOOL doesModelDataValidate = [self validate:&validationError];
if (doesModelDataValidate == NO) {
if (err) *err = validationError;
return nil;
}
//model is valid! yay!
return self;
}
相关文章
热门资讯
关注我们
精彩导读