这是我的代码：
MyTool tool = new MyTool(new SubTool());
tool.PrintingSystem.Document.Target = 1;
tool.ShowPreview();
我想知道是否可以像这样在初始化中填充PrintingSystem.Document.Target：
MyTool tool = new MyTool(new SubTool())
{
PrintingSystem.Document.Target = 1
};
当前不起作用。
答案 0 :(得分：3)
与对象初始化程序等效的原始代码为：
MyTool tool = new MyTool(new SubTool())
{
PrintingSystem = { Document = { Target = 1 } }
};
这只会为PrintingSystem调用 getters ，然后为Document，然后为Target调用 setter -就像您的原始代码。这是对象初始化器相对很少使用的功能，称为<嵌套对象嵌套初始化器。在ECMA C# standard中，第12.7.11.3节：
成员初始化程序，用于指定等号后的表达式，其处理方式与对字段或属性的赋值（第12.18.2节）相同。
在等号后指定对象初始化器的成员初始化器是 嵌套对象初始化器 ，即嵌入式对象的初始化。而不是为字段或属性分配新值，而是将嵌套对象初始化器中的分配视为对字段或属性成员的分配。嵌套对象初始化程序不能应用于具有值类型的属性，也不能应用于具有值类型的只读字段。
仅在PrintingSystem和Document默认为非空值的情况下才有效-否则，您需要根据fubo的答案设置属性。
答案 1 :(得分：1)
如果属性是一个对象，则引用另一个对象-您必须为每个对象创建一个新实例以避免{
"$schema": "./node_modules/@angular/cli/lib/config/schema.json",
"version": 1,
"newProjectRoot": "projects",
"projects": {
"socialscout": {
"root": "projects/socialscout/",
"sourceRoot": "projects/socialscout/src",
"projectType": "application",
"prefix": "app",
"schematics": {},
"architect": {
"build": {
"builder": "@angular-devkit/build-angular:browser",
"options": {
"outputPath": "dist/socialscout",
"index": "projects/socialscout/src/index.html",
"main": "projects/socialscout/src/main.ts",
"polyfills": "projects/socialscout/src/polyfills.ts",
"tsConfig": "projects/socialscout/tsconfig.app.json",
"assets": [
"projects/socialscout/src/favicon.ico",
"projects/socialscout/src/assets"
],
"styles": [
"projects/socialscout/src/styles.scss",
"projects/socialscout/src/custom.scss",
"projects/socialscout/src/theme.scss"
],
"scripts": [
"node_modules/progressbar.js/dist/progressbar.min.js"
]
},
"configurations": {
"production": {
"fileReplacements": [
{
"replace": "projects/socialscout/src/environments/environment.ts",
"with": "projects/socialscout/src/environments/environment.prod.ts"
}
],
"optimization": true,
"outputHashing": "all",
"sourceMap": false,
"extractCss": true,
"namedChunks": false,
"aot": true,
"extractLicenses": true,
"vendorChunk": false,
"buildOptimizer": true
}
}
},
"serve": {
"builder": "@angular-devkit/build-angular:dev-server",
"options": {
"browserTarget": "socialscout:build"
},
"configurations": {
"production": {
"browserTarget": "socialscout:build:production"
}
}
},
"extract-i18n": {
"builder": "@angular-devkit/build-angular:extract-i18n",
"options": {
"browserTarget": "socialscout:build"
}
},
"test": {
"builder": "@angular-devkit/build-angular:karma",
"options": {
"main": "projects/socialscout/src/test.ts",
"polyfills": "projects/socialscout/src/polyfills.ts",
"tsConfig": "projects/socialscout/tsconfig.spec.json",
"karmaConfig": "projects/socialscout/karma.conf.js",
"styles": [
"projects/socialscout/src/styles.scss",
"projects/socialscout/src/theme.scss"
],
"scripts": [],
"assets": [
"projects/socialscout/src/favicon.ico",
"projects/socialscout/src/assets"
]
}
},
"lint": {
"builder": "@angular-devkit/build-angular:tslint",
"options": {
"tsConfig": [
"projects/socialscout/tsconfig.app.json",
"projects/socialscout/tsconfig.spec.json"
],
"exclude": [
"**/node_modules/**"
]
}
}
}
},
"socialscout-e2e": {
"root": "projects/socialscout-e2e/",
"projectType": "application",
"architect": {
"e2e": {
"builder": "@angular-devkit/build-angular:protractor",
"options": {
"protractorConfig": "projects/socialscout-e2e/protractor.conf.js",
"devServerTarget": "socialscout:serve"
},
"configurations": {
"production": {
"devServerTarget": "socialscout:serve:production"
}
}
},
"lint": {
"builder": "@angular-devkit/build-angular:tslint",
"options": {
"tsConfig": "projects/socialscout-e2e/tsconfig.e2e.json",
"exclude": [
"**/node_modules/**"
]
}
}
}
},
"defaultProject": "untouchable-app",
"schematics": {
"@schematics/angular:component": {
"styleext": "scss"
}
}
}
NullreferenceException