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  • TypeScript: Week Reflection

    TypeScript: Week Reflection

    Introduction

    Type Script already provide decorators to help developers implement reflection.
    If we use the technique decorators, we have to add decorators on the target class during developing.
    But is there a way to find members of a specific instance?

    Here is a code to reflect an object instance by using JSON functions.
    The limitations:

    • Must provide an class instance
    • Cannot find members which have not be initialed.
    • Cannot find the class of a member
    • Only can provide typeof and isArray attributes.

    Source Code

    • Source
    export class ReflectMemberInfo {
        constructor(public name:string, public type: string, public isArray: boolean) {
        }
    }
    
    export class WeekReflector {
        members: ReflectMemberInfo[] = [];
        reflect(obj: any): void {
            JSON.stringify(obj, (key, value) => {
                if (key == '') {
                    // it is the root object
                    return value;
                }
    
                var isArray = (value instanceof Array);
                this.members.push(new ReflectMemberInfo(key, typeof(value), isArray));
                return null;
            });
        }
    }
    
    // Test
    class TestObject {
        memberBoolean: boolean = false;
        memberNumber: number = 1;
        memberString: string = "Jack";
        // memberSymbol: Symbol = Symbol();
        memberUndefined?: string = undefined; // type is undefined
        memberNull: string | null = null;   // type is object
        memberCannotFound: string;      // cannot be reflected
        memberObject: TestNestedObject = new TestNestedObject();
        // type is object
        memberStringArray: string[] = ["A", "B", "C"];      
        // type is object
        memberObjectArray: TestNestedObject[] = [new TestNestedObject(), new TestNestedObject()];
        // type is function
        memberFunction: Function = () => {};
        // cannot be reflected
        public normalFunc(): any {
            return null;
        }
        
    }
    
    class TestNestedObject {
        nestedNumber: number = 2;
        nestedString: string = "Mike";
        nestedNull: string | null = null;
        nestedUndefined?: string = undefined;
        nestedStringArray: string[] = ["A", "B", "C"];
    }
    
    var reflector = new WeekReflector();
    reflector.reflect(new TestObject());
    console.log(reflector.members);
    
    • Result
    [ ReflectMemberInfo { name: 'memberBoolean', type: 'boolean', isArray: false },
      ReflectMemberInfo { name: 'memberNumber', type: 'number', isArray: false },
      ReflectMemberInfo { name: 'memberString', type: 'string', isArray: false },
      ReflectMemberInfo { name: 'memberUndefined', type: 'undefined', isArray: false },
      ReflectMemberInfo { name: 'memberNull', type: 'object', isArray: false },
      ReflectMemberInfo { name: 'memberObject', type: 'object', isArray: false },
      ReflectMemberInfo { name: 'memberStringArray', type: 'object', isArray: true },
      ReflectMemberInfo { name: 'memberObjectArray', type: 'object', isArray: true },
      ReflectMemberInfo { name: 'memberFunction', type: 'function', isArray: false } ]
    
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  • 原文地址:https://www.cnblogs.com/steven-yang/p/7731874.html
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