摘要：好了，廢話不多說(shuō)，今天來(lái)說(shuō)一說(shuō)修改器。前兩天看一同事好像對(duì)這個(gè)修改器了解不多，所以今天就拿它作為入口，扒一扒其實(shí)現(xiàn)源代碼。前端就可以直接拿到結(jié)果同樣的，還有方法來(lái)定義一個(gè)修改器。

感覺(jué)好長(zhǎng)時(shí)間沒(méi)寫東西了，一方面主要是自己的角色發(fā)生了變化，每天要面對(duì)各種各樣的事情和突發(fā)事件，不能再有一個(gè)完整的長(zhǎng)時(shí)間讓自己靜下來(lái)寫代碼，或者寫文章。

另一方面現(xiàn)在公司技術(shù)棧不再停留在只有 Laravel + VUE 了，我們還有小程序、APP 等開發(fā)，所以我關(guān)注的東西也就多了。

接下來(lái)我還是會(huì)繼續(xù)持續(xù)「高產(chǎn)」，把寫技術(shù)文章當(dāng)作一個(gè)習(xí)慣，堅(jiān)持下去。

好了，廢話不多說(shuō)，今天來(lái)說(shuō)一說(shuō)「Eloquent： 修改器」。

一直想好好研究下 Eloquent。但苦于 Eloquent 有太多可研究的，無(wú)法找到一個(gè)切入點(diǎn)。前兩天看一同事好像對(duì)這個(gè)「Eloquent： 修改器」了解不多，所以今天就拿它作為入口，扒一扒其實(shí)現(xiàn)源代碼。

首先還是拿一個(gè) Demo 為例：

birthday);
        return Carbon::now()->diffInYears($date);
    }
}

這個(gè)代碼比較簡(jiǎn)單，就是通過(guò)已有屬性 birthday，計(jì)算 Baby 幾歲了，得到 age 屬性。

前端就可以直接拿到結(jié)果：

return $baby->age;

同樣的，還有 setXxxAttribute 方法來(lái)定義一個(gè)修改器。

讀代碼還是從使用入手，如上通過(guò) $baby->age 調(diào)用 age 屬性，這個(gè)屬性沒(méi)在類中定義，所以只能通過(guò) PHP 的魔術(shù)方法 __get() 調(diào)用了。

我們看看 Model 類的 __get() 方法：

/**
 * Dynamically retrieve attributes on the model.
 *
 * @param  string  $key
 * @return mixed
 */
public function __get($key)
{
    return $this->getAttribute($key);
}

好了，我們開始解讀源代碼了：

/**
 * Get an attribute from the model.
 *
 * @param  string  $key
 * @return mixed
 */
public function getAttribute($key)
{
    if (! $key) {
        return;
    }

    // If the attribute exists in the attribute array or has a "get" mutator we will
    // get the attribute"s value. Otherwise, we will proceed as if the developers
    // are asking for a relationship"s value. This covers both types of values.
    if (array_key_exists($key, $this->attributes) ||
        $this->hasGetMutator($key)) {
        return $this->getAttributeValue($key);
    }

    ...
}

重點(diǎn)自然就在第二個(gè) if 上，主要判斷 attributes 數(shù)組中是否包含該屬性，如果沒(méi)有，則會(huì)執(zhí)行函數(shù) $this->hasGetMutator($key)：

/**
 * Determine if a get mutator exists for an attribute.
 *
 * @param  string  $key
 * @return bool
 */
public function hasGetMutator($key)
{
    return method_exists($this, "get".Str::studly($key)."Attribute");
}

這就對(duì)上了我們的 Demo 中自定義的函數(shù) getAgeAttribute()，也就返回 true 了。

接下來(lái)就是執(zhí)行函數(shù) $this->getAttributeValue($key),進(jìn)而執(zhí)行函數(shù)：return $this->mutateAttribute($key, $value);

/**
 * Get the value of an attribute using its mutator.
 *
 * @param  string  $key
 * @param  mixed  $value
 * @return mixed
 */
protected function mutateAttribute($key, $value)
{
    return $this->{"get".Str::studly($key)."Attribute"}($value);
}

好了，到此我們基本就知道了獲取自定義 Attribute 的流程了。

相信解析 set XxxAttribute 也是很簡(jiǎn)單的。

好長(zhǎng)時(shí)間沒(méi)寫東西了，先從最簡(jiǎn)單的入手，練練手。解析 Eloquent 需要費(fèi)很多腦細(xì)胞，接下來(lái)的一段時(shí)間我會(huì)圍繞著這個(gè)主題好好研究下去，盡可能的全部解讀一遍：：

.
|____Capsule
| |____Manager.php
|____composer.json
|____Concerns
| |____BuildsQueries.php
| |____ManagesTransactions.php
|____Connection.php
|____ConnectionInterface.php
|____ConnectionResolver.php
|____ConnectionResolverInterface.php
|____Connectors
| |____ConnectionFactory.php
| |____Connector.php
| |____ConnectorInterface.php
| |____MySqlConnector.php
| |____PostgresConnector.php
| |____SQLiteConnector.php
| |____SqlServerConnector.php
|____Console
| |____Factories
| | |____FactoryMakeCommand.php
| | |____stubs
| | | |____factory.stub
| |____Migrations
| | |____BaseCommand.php
| | |____FreshCommand.php
| | |____InstallCommand.php
| | |____MigrateCommand.php
| | |____MigrateMakeCommand.php
| | |____RefreshCommand.php
| | |____ResetCommand.php
| | |____RollbackCommand.php
| | |____StatusCommand.php
| |____Seeds
| | |____SeedCommand.php
| | |____SeederMakeCommand.php
| | |____stubs
| | | |____seeder.stub
|____DatabaseManager.php
|____DatabaseServiceProvider.php
|____DetectsDeadlocks.php
|____DetectsLostConnections.php
|____Eloquent
| |____Builder.php
| |____Collection.php
| |____Concerns
| | |____GuardsAttributes.php
| | |____HasAttributes.php
| | |____HasEvents.php
| | |____HasGlobalScopes.php
| | |____HasRelationships.php
| | |____HasTimestamps.php
| | |____HidesAttributes.php
| | |____QueriesRelationships.php
| |____Factory.php
| |____FactoryBuilder.php
| |____JsonEncodingException.php
| |____MassAssignmentException.php
| |____Model.php
| |____ModelNotFoundException.php
| |____QueueEntityResolver.php
| |____RelationNotFoundException.php
| |____Relations
| | |____BelongsTo.php
| | |____BelongsToMany.php
| | |____Concerns
| | | |____InteractsWithPivotTable.php
| | | |____SupportsDefaultModels.php
| | |____HasMany.php
| | |____HasManyThrough.php
| | |____HasOne.php
| | |____HasOneOrMany.php
| | |____MorphMany.php
| | |____MorphOne.php
| | |____MorphOneOrMany.php
| | |____MorphPivot.php
| | |____MorphTo.php
| | |____MorphToMany.php
| | |____Pivot.php
| | |____Relation.php
| |____Scope.php
| |____SoftDeletes.php
| |____SoftDeletingScope.php
|____Events
| |____ConnectionEvent.php
| |____QueryExecuted.php
| |____StatementPrepared.php
| |____TransactionBeginning.php
| |____TransactionCommitted.php
| |____TransactionRolledBack.php
|____Grammar.php
|____Migrations
| |____DatabaseMigrationRepository.php
| |____Migration.php
| |____MigrationCreator.php
| |____MigrationRepositoryInterface.php
| |____Migrator.php
| |____stubs
| | |____blank.stub
| | |____create.stub
| | |____update.stub
|____MigrationServiceProvider.php
|____MySqlConnection.php
|____PostgresConnection.php
|____Query
| |____Builder.php
| |____Expression.php
| |____Grammars
| | |____Grammar.php
| | |____MySqlGrammar.php
| | |____PostgresGrammar.php
| | |____SQLiteGrammar.php
| | |____SqlServerGrammar.php
| |____JoinClause.php
| |____JsonExpression.php
| |____Processors
| | |____MySqlProcessor.php
| | |____PostgresProcessor.php
| | |____Processor.php
| | |____SQLiteProcessor.php
| | |____SqlServerProcessor.php
|____QueryException.php
|____README.md
|____Schema
| |____Blueprint.php
| |____Builder.php
| |____Grammars
| | |____ChangeColumn.php
| | |____Grammar.php
| | |____MySqlGrammar.php
| | |____PostgresGrammar.php
| | |____RenameColumn.php
| | |____SQLiteGrammar.php
| | |____SqlServerGrammar.php
| |____MySqlBuilder.php
| |____PostgresBuilder.php
| |____SQLiteBuilder.php
| |____SqlServerBuilder.php
|____Seeder.php

Eloquent： 修改器 https://laravel-china.org/docs/laravel/5.7/eloquent-mutators/2297

__get()使用說(shuō)明 http://php.net/manual/zh/language.oop5.overloading.php#object.get

未完待續(xù)